The story is centered around Anna, an uber talented violinist going through mental health issues in the wake of her instant success. Her performance on YouTube alone has been viewed by millions. Not believing in herself and her abilities, Anna has not been able to play a complete a piece, since every mistake she makes, she has to start all over. With the advice of her therapist to try something new, and her recent long term boyfriend asking for an open relationship, Anna ventures into the world of dating apps to find a no-strings attached relationship.

There she meets Quan and though the attraction was palpable, their relationship blossoms ever so slowly and with lots of mistakes in it, yet each of them willing to forgive and try again.

Quan is a very successful children’s clothing designer and has his own set of struggles. He has just gone through some health issues and recent surgery. He is not only gorgeous, but he is a kind soul. Unfortunately, his tattooed exterior that goes through his body and neck, and with his motorcycle loving persona, many have made their impressions on him based on his appearance rather than getting to know him and finding out what a kind, generous and selfless human being he really is. The character development is spot on, and their flaws and imperfections made me love Anna and Quan even more.

I loved THE HEART PRINCIPLE! It exceeded all my expectations for a contemporary romance read that had so much more. Hoang addressed themes of mental health, a character in the autism spectrum, the Asian family expectations and parent-child relationships, stereo types against people with tattoos, and a family affected by a tragic and devastating illness.

As a stroke nurse, I thought Hoang captured what survivors and families go through a stroke – it was spot on. I was moved to tears by some of the feelings and true to life situations – it was written so beautifully with such sensitivity and grace.

I cannot stop recommending this novel.

Fans of angsty romance will be delighted with The Heart Principle, the third book in Helen Hoang’s The Kiss Quotient series.  While this book – and therefore this review – does contain spoilers for the first two novels, you do not have to read those to enjoy this story.

Quan Diep, older brother to the hero (Khai) from The Bride Test and cousin and best friend to the hero (Michael) from The Kiss Quotient, has beaten his testicular cancer but not without some permanent scars, both physical and emotional. One of the hurdles on his way back to normal is dating, something he used to take great joy in but hasn’t done in years. He’s not ready to get back into the full-blown girlfriend/boyfriend thing but on Michael’s advice, he decides to pick someone from a dating app to hook up with.

Violinist Anna Sun is on a leave of absence from her job. A YouTube video shot her to unanticipated fame and the result has been an incapacitating neurosis which has her caught between fan expectations and her own perceived inability to meet them. Naturally, this is the perfect moment for her longtime boyfriend Julian to announce he wants an open relationship. An understandably angry Anna warns him that if he dates others, she will too. He smirks confidently at her and says :

“I don’t think you’ll sleep with someone else. I know you, Anna. . .  You don’t like sex.”

But Anna is resolved and places her photo on a dating app, with the tag,

“Looking to spend an uncomplicated evening with someone nice. Just one night, please.”

After scrolling through numerous non-starters for his own one-night stand, Quan comes across Anna’s profile. He likes her directness and the no-strings attached nature of what she is looking for and messages her. She responds immediately but the encounter isn’t what he expected. They end up watching the end of a documentary together via text, bonding over the sweetness of the film before deciding to meet up the next night.

Anna arrives at the agreed upon restaurant but when she sees Quan get off his motorcycle she panics, races to the bathroom and spends half an hour in a stall ignoring the many texts he sends. Once her phone goes silent, she risks sneaking out but of course runs into him in the hall as he heads to the men’s room. Anna apologizes before once more running away, but when Quan reaches out to check up on her, she responds. They wind up syncing their videos and texting as they watch another documentary and thus their relationship is launched.

I felt that, compared to the other two novels in the series, this story got off to the most romantic start.  Somehow, Quan and Anna turn meeting through a dating app into a meet cute that is absolutely amazing. Equally charming is the arc taken by their love story. Quan is astonishingly patient with the skittish, painfully shy and awkward Anna. They never wind up having that one-night stand because Anna can’t bring herself to do it, and Quan delightfully works on building an emotional relationship with her before moving on to the physical. As in The Kiss Quotient, the hero’s patience and kindness make a huge difference to the heroine’s attitude towards sex. Anna blossoms due to Quan’s ability to dole out physical intimacy in a slow, measured manner that both lets her process her responses and gives her time to enjoy the experiences. I loved that their emotional and physical connections were in lock step, advancing together.

While the other two stories have some serious threads running through them, The Heart’s Principle is understandably the most poignant of the series. Quan is dealing with the aftermath of his illness, not just the physical changes to his body but the impact that will have on his future romantic relationships.

Anna’s plate is overflowing with trauma. Her neurosis/anxiety regarding her playing has essentially stripped her of her ability to work and taken away something she used to enjoy.  Her family situation is difficult because her mother never wanted Anna to pursue a career in music, making it a point to tell her how impractical that was and how Anna’s inability to master any other skills left her vulnerable to being a complete failure. Her older sister Priscilla is controlling and manipulative, so she has no one to turn to for support among her relatives. Anna also feels like a fish out of water; she spends all her time trying to read other people and do whatever pleases them and feeling like she never gets it quite right. When her therapist diagnoses her with autism about halfway through the story, it is actually a relief for Anna to finally have a name for what has made her feel like an outsider her whole life.

All of that would have been enough for Quan and Anna to work through, but the last half of the book ups the angst factor considerably by having a family tragedy occur and forcing Anna to return to her parents’ home to be a caregiver to a close relation. Being there places Anna in constant proximity to her mom and Priscilla, the latter of whom makes it clear that Anna is far less than she should be – less smart, less capable, less strong. While Quan is everything that one could have hoped for in that situation – loving, supportive, unbelievably kind and caring – Anna gets buried in an avalanche of emotional, physical and mental exhaustion by the demands of caregiving under the hyper-critical eye of her family. It leads her – and those of us going through it with her - to a very grim place.

Naturally it puts a strain on the romance. Not just the fact that Anna is going through so much and Quan is trying to provide long distance (several hours away) support, but the fact that Anna’s family starts pushing him into ‘fling’ status and tries to force Anna to take back Julian.  All told, this thirty percent or so of the book is super intense. And frankly, it lasts too long. Anna and Quan’s love story is nearly swallowed whole by Anna’s journey through some incredibly difficult, depressing life situations.

I’ve encountered this before in romance novels. Some authors seem to feel as though their couples have to earn an HEA by going through fire together and this book certainly does that. It feels somewhat  incongruous that the sweet romance at the beginning and the lovely one at the end goes through such a difficult middle portion, but the author does a great job of tying her tale together. The length of Anna and Quan’s trial by fire is a bit too extended, but it does showcase that they are genuinely, deeply in love and will absolutely be able to survive any future tests to their relationship life throws at them.

Overt extended trauma aside, I enjoyed The Heart Principle. It’s deeper, darker and more serious than the first two books in the series at times, but readers who can take some pain with their pleasure will find a lot to love here.

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Let me start by saying that I am so, so happy Helen Hoang was able to write the book she wanted and needed to write. Her author’s notes always touch me, but this one was especially poignant. Hoang crafts undeniably beautiful books with imperfect characters you will both relate to and root for and THE HEART PRINCIPLE was no exception.

Anna and Quan’s book hit me right in the solar plexus. From our first meeting with Anna and her detestable boyfriend, I knew this book would grip me from start to finish. Anna’s emotional journey was heart-wrenchingly, achingly real. My heart literally hurt for her at parts.

While I feel this book is very much Anna’s journey, the romance and Quan are still a central and integral part of the plot. Is this book heavy? Yes. Does it tackle multiple serious and important plot points? Absolutely. But it has light moments and sexy parts that help balance the overall tone of the book. Quan is essential to those lighter moments. Quan was everything. Fans of this series have been waiting on his book, and while he has had some bumps and bruises both emotionally and physically since the last book, it only served to make him a better partner to Anna. He’s strong and funny and the solid rock we all want our book boyfriends to be. Plus, he’s super hot? That’s a given, right? When he pulls up on his motorcycle for his first date with Anna? WHEW. HOT.

The relationship between Anna and Quan felt modern and fresh and, honestly, relatable. Anna’s boyfriend wants to be in an open relationship and starts dating other women, so Anna gets on a dating app. From first date anxiety to hook-up culture to awkwardly intimate conversations with strangers online, dating is tough – Anna was lucky she found Quan on her first try!

There is a lot of discussion around this book, for good reason. I read this book weeks ago and I still can’t get it out of my head. I agonized over this review because the book dug up so much emotion in me. The themes of family guilt and expectations, especially within Asian culture was fascinating. Adding in Anna’s diagnosis and the ripple effect through her family, there was a lot going on and it was all handled with a deft and empathetic hand.

Now, was this a five star book for me? Sadly, no. I did love it, but the ending was so incredibly rushed and almost frantic that I felt a little overwhelmed. I think the pacing was a little off. The caretaking scenes were vital, but they took up so much page time that I felt a little shortchanged by the last 10% of the book.

I also had difficulty with Anna and Quan’s emotional connection at the end. It was there at the beginning, but the relationship was so incredibly one-sided. Relationships are often uneven, and partners help you carry the emotional load, but I wanted Anna to help Quan occasionally. Or at least listen to him? There was a part of the book I noted that Anna didn’t even know what Quan did for a living (which, happens to be his passion) well into their dating journey. Additionally, when Quan has struggles at said job, he solves them without Anna getting involved at all. It made their journey feel like two parallel tracks rather than an ultimate merge. Much of their relationship happens off-screen and I think the romance ultimately suffers for it.

I kept this at four stars because it’s a really, really good book, and I adore the idea that the characters we grow to love don’t have to have it all figured out at the end of the book for there to still be a happy and hopeful ending. Oftentimes, emotional struggles last a lifetime and imperfect people deserve to find love and relationships too.

Overall, this was a beautifully written book that I will continue to think about for months to come.

TW: Grief, caretaking, loss of a parent, suicidal thoughts

**I received a free copy of this ebook in order to provide an honest review**

This book is absolutely beautiful. I have loved all of Helen Hoang's books so far and this book is no exception.

The Heart Principle follows Anna, a woman who is struggling to follow her passion and suffocating under immense pressure from her family. She meets Quan, a man who is trying to reconnect with himself and others after he has recovered from health issues.

Seeing Anna's struggles was extremely difficult, but I found myself feeling connected to her character in a way that I have never felt before. She is so driven to please people that she has lost sight of who she is as a person. Her journey of self discovery and healing was incredibly motivating for me to see and has inspired me to do things for myself more and less for what other people want.

Her relationship with Quan was anything but easy with all of the added outside pressure but it was beautifully developed. I loved them together. They really helped each other feel more secure with themselves and pushed each other to be the best version of themselves. I found myself yearning for a relationship like that every time they interacted.

If you have read previous books from Helen Hoang, just keep in mind that this one is very different. It is much more emotional than her previous books and deals much more with self-discovery and acceptance than it does with romance.

With that being said, it is absolutely worth every second of heart-ache. Do yourself a favor and read this wonderfully written story.

Thank you to NetGalley and Berkley for allowing me to read an ARC of this book in exchange for an honest review.

I have been anticipating the Heart Principle for years now. I loved Kiss Quotient and the Bride Test, but this one might be my favorite.
Quan stole my heart in both Kiss Quotient and The Bride Test. He is so accepting and just a genuinely nice guy. I knew I would love him, but even I underestimated just how much! Quan is just the best; I don’t know how else to describe him. I also loved Anna. Her struggles were relatable, and I loved how strong she ended up being. The way that Quan was with her and how she was able to let him in. These two really found what they needed in each other.
Like the other books Hoang has written, Anna is likely on the autism spectrum. I think out of the three, this one tackles a lot of issues associated with that and many mental health issues. Many characters, including Anna and Quan, suffer from mental health issues, and I appreciate that this book did not shy away from that.
I loved everything about this book, and I hope there is more from this author!

The Heart Principle is the third book in the Kiss Quotient series, though each can be read as a stand-alone.
This book follows Anna and Quan, who we've met before in the previous books. Anna is a violinist who is struggling to play music after finding online fame with a viral video. Her long-term boyfriend has also suggested that they have an open relationship before getting married. Anna decides to have a one-night stand with Quan, who she met on a dating app. But when the one-night stand fails they decide to meet up again...and again...and again.

First of all, this book is different than the other two as it is written in dual first-person POV and not third person. The whole vibe and plot are also heavier than it has been and while I still loved the book, it was not as fun to read as The Kiss Quotient.

I loved Quan as a lead finally. He was so lovely and caring, though I wish he was the focus of the story a little more. It feels like mostly Anna's story, not Quan. Not a bad thing because I did enjoy Anna, I just wanted some more Quan.

I felt the ending was lacking just a tiny bit. The book moved so fast during the 'After' portion and I wish we were given more time to see Quan and Anna's relationship grow instead of having it kind of summarized in later chapters.

Overall, another win by Helen Hoang who is definitely an instant buy author from me now.

Ms. Hoang does it again with another great story. The Heart Principle is a heavier read. Anna & Quan are both dealing with some tough stuff.

Ms. Hoang's put her heart on her sleeve when sharing this story. The first part of the book is about Anna's current boyfriend who wants an open relationship before he settles down with her - just make sure he isn't missing out on anything. At the same time, Quan is coming to terms with something that leaves him not feeling totally himself.

The two meet through a dating app and start out texting and watching nature documentaries together. They both agree to a no-strings-attached one-night-stand but don't actually do the deed just yet. Neither one wants to admit to not wanting their relationship to be over so they hold off because once the deed is done then their relationship is over.

During the middle part of the book, Anna is experiencing caretaker burnout as she cares for her ill father. Along with being diagnosed with autism and having her sisters think she's vying for attention. Quan is trying to make a go with his business and he's running into roadblocks.

In the last part of the book, the reader sees Anna & Quan's relationship grow as their intimate feelings towards each other become more intense. Anna's boyfriend, from the first part of the book, returns and is ready to settle down now that he's "sowed his seed". His return throws a wrench in Anna's life. She's at the point where she has hit rock bottom in dealing with what life has thrown at her and isn't ready to deal with his return.

Here's where Quan & Anna declare their love for each other. The ex-boyfriend is that catalyst that helps them know this isn't a casual thing but a forever thing.

Their love story was one that has a lot of heart.

The author's note at the end of the book reveals that even though this is fiction it is also a half memoir. Up to this point in Ms. Hoang's books, this is the book that contains the most about her. Ms. Hoang and Anna share struggles, pain, and shame. And that's why I say - Ms. Hoang put her heart on her sleeve when she wrote this book.

I can't get enough of this series!! Each book is so good!!

this was fine, nothing very memorable about it but also nothing that made me fully dislike the it. I feel like I liked the characters way more separately than together… I just didn’t feel the chemistry between them and it felt very much lie insta love for me. I would’ve appreciated some longer development.

I do always love the representation in Helen Hoang’s books and this one wasn’t different! It was definitely one of the best parts of the book.

This was by far my favorite in the series. Helen Hoang just knows how to write the perfect thought-provoking, yet steaming hot romance novel. Could not put it down!

The trilogy comes to an end, and what an end it was! @hhoangwrites, thank you for these stories & representation. I highly recommend reading the author’s note before you dive into this one (and will have some good content warnings). ⁣
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I hesitate to call THE HEART PRINCIPLE heavy, because the characters go through very real-life things — sickness, death of a parent, anxiety, and unsupportive family, all while trying to find someone who to weather the storms with.⁣
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Anna and Quan have my heart for their vulnerability, patience, and understanding for each other. 🤍

The Heart Principle is a very sweet, but heavy romance. It stars Anna, a concert violinist after her boyfriend Julian decides he’s wants to sleep around before settling down with her. She decides if he can do it, so can she!

She meets tattooed Quan on a dating app and decides to have a one night stand with him. Except it doesn’t go as planned and they have a 2nd and 3rd date. They really hit it off just as a family tragedy happens and Anna is buried under family stress and trauma. Her ex also comes back during this time and threatens to mess up everything she has with Quan.

Anna struggles a lot with her role in her family (some of which is cultural, some of which she’s human doormat) and her place in relationship with Julian. When she meet Quan, they are on an even playing field and it just goes so much smoother. He understands her quirks and personal needs.

I did enjoy her time talking about her violin and her struggles with the music. I especially loved when she picks her new violin. 🎻

CW: This book does have a significant portion where a parent gets sick and eventually passes. I handle this stuff better than I used to, but this is a warning to all members of the dead parent club.

Absolutely stunning. Not what I expected, but so much more. I'm not sure what to even say, except that I read this in two days and stayed up crying to finish it. I am already looking forward to whatever Helen Hoang writes next.

"The Heart Principle" is the third title in Helen Hoang's Kiss Quotient series. It can be read as a standalone.

Thank you to NetGalley & the publisher for the eARC.

I read this one Saturday and finished the whole book in one day because I couldn’t put it down. As a mom ofa toddler, this rarely happens but I snuck in reading time every spare moment I could find, because it was that good! Helen Hoang has been a favorite and an autobuy author for me ever since I read The Kiss Quotient a few years ago. I think you can really tell how much she puts of herself in her books. I really appreciate her authors notes and make sure to read them.
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Anna’s boyfriend Julian decides he wants to date other people before settling down. She decides to date too and tries a dating app so she can have a one night stand. Instead she and Quan have a few tries and develop feelings for each other. There is a lot going on in Anna’s life. Will she and Quan overcome these to be together? ⁣
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I was instantly drawn into Anna and Quan’s lives. I loved the alternating chapters between the two of them. Quan is definitely book boyfriend goals. Anna’s family was quick to judge him because of his tattoos but he was sweet, supportive, successful, and so patient. It helped that he had an autistic sibling as Anna learns partway through the book that she is autistic. There were so many heartbreaking moments of this book. My heart broke for Anna when she was helping to care for her dad and exhausting herself by constantly masking. I felt heartbroken for her but also a little relief that she and her father were free when he passed away. I am a huge fan of Helen Hoang and I'm so glad I pre-orded a copy because this is one of the best books I've read this year.

I really liked The Kiss Quotient, I totally enjoyed The Bride Test, and I LOVED The Heart Principle. It is absolutely Hoang's best book to date. The story felt so incredibly genuine and after reading the author's note, it's clear this is because this story is inspired by Hoang's own experiences with autism, being a caregiver to a family member, and dealing with loss. The care and heart that Hoang so clearly put into this story pays off. I laughed, I cried, I blushed. My only small complaint is that the last bit of the book felt rushed. I wanted to be a part of Anna and Quan's life a little longer, but that's the best kind of complaint that you can have with a book like this.

*Swoon* I absolutely loved everything about this book. I haven’t read the first two books in this series but I hope to very soon. I was expecting a cute little romcom, but this book was much deeper than that and I think that’s what made me love it so much. Anna and Quan’s chemistry felt so real. Both main characters are dealing with deep internal struggles and I adored how patient and sweet they were toward one another. I 100% recommend reading the author’s note too - Helen based a lot of this book on her own life.

I can’t wait to read the first two books and I have a feeling Helen Hoang will become an auto buy author for me.

Short Review: I was not expecting this book to make me cry. It did. I loved it so much.

Long Review: Let's just address the obvious. Helen Hoang is the queen of romance. She just is. No question.

This book has it all. It's real, raw, messy and human. The characters quickly grab your heart and don't let go. They become people you see bits of yourself inside. Hoang has taken the deeper topics of love, death, grief, and disability and weaved them into a beautiful story of overcoming fears, standing up for who you are, and finding love.

All the feels. Loved it.

I really enjoyed Hoang’s previous books and was super excited to be able to read this on my Kindle via NetGalley (thank you, Net Galley!) I wasn’t sure what to expect because the author’s note and promo specifically said it was NOT the same as her previous two. Well, there were certainly were differences, but also similarities. Again, a protagonist who has an Autism Spectrum Disorder, some familiar characters from the previous two novels, a steamy romance with some pretty matter of fact explicit sex scenes, and a strong cultural emphasis. Since those were all things I liked in the first two, I’m glad they still existed in this one.
This was terrific, I’d say a big difference is that when I think about this I think it was really sad. (spoilers ahead, so if you don’t want to know what happens you can stop here and safely know-this was really good and I really enjoyed it, but don’t expect a sexy fun romance.)

OK, here we go. Her family’s treatment of her and reaction to her diagnosis (which was enlightening and liberating to her) was just tragic, I thought. They treated her like garbage and it’s no wonder her mental health suffered. Her father’s demise was so sad. I just can’t believe anyone thought that was a good way to keep him alive and again, to treat Anna the way they did. It quickly turned into an all out family tragedy, I thought. Pacing wise it was a little strange how the final third (maybe less) of the book was sort of quickly racing through time (suddenly at the end it’s two years later? It almost felt more like a thorough outline of the plot.) More like a very long epilogue. And then you read the author’s note and it all makes sense. Just a lot of sadness here and I wanted to offer Hoang a hug.

Very good.

How does every book she write get better and better?? I love this whole series. I think the best part is the diverse characters with different struggles. I love that she opens people's eyes to characters that have autism. Every character expresses it so differently. Keep writing Helen!

This book was so personal, and in a way that I didn’t know it could be. It was also incredibly triggering, and no review of this book could have prepared me for what I was going to go through. It was too oddly specific and hit close to home.

Because there is my an option to bypass the star ratings on here, I’m conflicted with how I want to rate it. Just because this book affected me as it did, doesn’t mean it was bad or that someone else shouldn’t give it a try. For books I DNF, I give them a one-star rating, but Helen wrote a book that I hope has helped her heal and I won’t undermine that. The writing was still so great, but I personally can’t say I enjoyed it. I’m stuck.

My rating/review will never be able to properly describe this book, but I hope people really look at reviews before jumping into this one. It’s not like the previous two, with a slightly more light-hearted approach. However, it still tells an important story.

I really enjoyed Helen Hoang's latest book. The set up was fun and both Anna and Quan were very likeable characters, even more so when paired together. Unlike some of the recent romance novels out there, this one dealt with some really dark material like caregiving for a sick family member and difficult family relationships, but all of it was handled really well in the book. My only complaint about the book is that there is one chapter where Quan abruptly does a crazy Grand Canyon run and that really took me out of the whole story because of how random it was. When he returns, the plot regulates back to normal, but that one chapter was very jarring.