This book hit a spot for me and I’m officially a John McMahon fan!

I will be reading any PAR unit books from here on out.

Thank you for the opportunity to preview Head Cases. This is a police procedural novel that centers on an elite FBI group and a lead investigator.
I think this will be a series as although this novel is wrapped up at the end there Is certainly enough interesting information about this FBI group to provide more cases.
There’s a lot to digest and follow in this case of a murder and a supposed defunct serial killer.
Great detective work is outlined and a lot of characters to follow.
If you enjoy the intricacies of detective fiction this is a good read.
3.5 stars

Thank you so much to netgalley and the publisher for the arc of this one in exchange for an honest review!

This book follows a FBI agent who is part of the PAR unit. He is very smart and a bit different than most people. The whole unit is full of people who have special skills but are not necessarily the best socially.

In this book, we follow a case that involves a serial killer who kills serial killers and taunts the police. We follow the team as they try to catch the killer.

I really enjoyed this book! I loved all the unique characters and situations that they were in. The investigation kept me guessing throughout.

I wanted to be an FBI agent when I was little so this book was right up my alley. If you like Criminal Minds or investigation books, this one is for you!

I can't wait to read the next book when it comes out next year!

I honestly love detective lead thrillers and this one was so much fun. A serial killer, hunting serial killers? Sign me up. Gander Camden was such a fun character, as were the rest of the PAR Unit. I loved how because of their uniqueness, they got their own department in the FBI. The twists in this book amazing and the pacing was great. I am so excited this is the first book in this series, so we will get more!! The audiobook was also amazing and really added a lot of character to the story.

Someone is playing vigilante and killing serial killers. The first one was a man about to be indicted for three murders when his house caught fire and a body assumed to be him was found. That was seven years ago and he had been free to roam the country and continue his killing spree until the new killer found him. The second case was a killer who had just been paroled after decades behind bars.

PAR is the Pattern And Recognition unit of the FBI. Gardner Camden works in the unit, sharing with the others some miscue in his career that didn't warrant dismissal but made it better if he was forward facing with the public. In his case, it was turning in his beloved wife when he found she and her boss were defrauding a bank, giving his partner, a respected FBI agent and her father, a heart attack. In others, it was disrespect, hitting on the wrong woman, or other mistakes.

Everyone in PAR has a unique talent. Gardner has an eidetic memory and sees patterns where others do not. His partner, Cassie, has the same pattern sensing ability but more on the mathematical side. Another woman is an Olympic level sharpshooter. Frank runs the unit and focuses on the big picture. Gardner is on the spectrum and the only person who really understands him is his mother but she is now hospitalized with dementia.

To his surprise, Gardner is put in charge of the case, going over Frank's head. Gardner was the person who had identified the first killer seven years ago and the Director feels that he would have an advantage on finding the killer who believes his mission is to kill other killers. As the case progresses, it becomes evident that the killer knows much about Gardner's life and that his plan is to also kill off prominent FBI members. Can Gardner find him?

This is the first book in a new series by the author, who works in marketing when not writing thrillers. He has another series also. In this one, the pace is fast and furious, perhaps a bit too frantic but quite engaging. I'm looking forward to seeing where the PAR unit goes and more of Gardner's life. This book is recommended for mystery readers.

Thank you to Netgalley, St. Martin’s Press | Minotaur Books and John McMahon for providing this book for review. All opinions are my own.

From the opening chapter, Head Cases delivers full-on Criminal Minds vibes with its ensemble of brilliant, quirky FBI agents in the Patterns and Recognition (PAR) unit. Your inner profiler will be hooked from the start.

When DNA evidence links a murder victim to a serial killer previously presumed dead, the PAR team swings into action. Their leader, Gardner Camden, is a genius haunted by his own brilliance—giving serious Spencer Reid energy. Alongside him is a powerhouse crew: a mathematician, a weapons expert, a computer whiz—all working in sync to crack the case. The killer taunts them with puzzles and riddles, making this an intensely cerebral game of cat and mouse.

What I loved most:

Team dynamics: The chemistry between Camden and his colleagues is authentic and engaging. I loved the way their personalities balanced each other.

Twisty suspense: The puzzles are smart, the case is chilling, and the tension keeps climbing.

Atmosphere: McMahon crafts just the right amount of darkness and intensity without losing the character-driven focus.

Head Cases is smart, fast-paced, and packed with pulse-pounding twists. The ending completely surprised me—in the best way. I truly hope this becomes a full series because I would absolutely follow the PAR team through more cases. If you’re a fan of psychological thrillers or FBI procedurals, you’ll love this one.

I really enjoyed this book and the characters trying to find a serial killer. They are a rag tag team which the fbi is trying to eliminate but will they be able to catch the killer before the team is disbanded?

"𝑴𝒚 𝒂𝒄𝒕𝒔 𝒂𝒓𝒆 𝒅𝒊𝒔𝒕𝒓𝒂𝒄𝒕𝒆𝒅 𝒃𝒚 𝒎𝒚 𝒐𝒘𝒏 𝒄𝒐𝒏𝒔𝒄𝒊𝒆𝒏𝒄𝒆."

Special thanks to @johnmcmahonbooks @minotaur_books & @negalley for the #gifted eARC.

👉🏼 swipe for synopsis ➡️

𝙈𝙔 𝙍𝙀𝙑𝙄𝙀𝙒:
⭐️⭐️⭐️⭐️💫

Don't read this if you're quesy easily, especially with explained body parts are concerned.

This one had my mind engulfed with every page and case that appeared.

I love a good serial killer novel but this one is AMAZING. It's intense suspenseful and down right unputdownable. I'm so invested in the case and in Gardner's life.

Great police procedural and game of cat and mouse that leaves your reeling til the very end.

𝙋𝙐𝘽 𝘿𝘼𝙔:
January 28, 2025

ℚ𝕆𝕋𝔻❓️⁉️❓️
What's your thoughts on police procedurals?
Love them, hate them, havnt found the right one for you yet?

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#mysteryandthrills #thrillersandsuspense #thrillerfriendsunite #thrillerlover #thrilleraddict #thrillerjunkie #thrillergirlie #bookbuzz #headcases #policeprocedural #fbi #johnmcmahon
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MY VERDICT:
Atmospheric thriller with a complex protagonist, but too convoluted for my taste.

Head Cases tells the story of a unique FBI team that tracks down killers.
The main character is Agent Gardner Camden, a brilliant puzzle-solver who is really good at connecting the dots.
He works with the fictional PAR (Patterns and Recognition) unit, a group that tackles the toughest unsolved cases. That’s where the book’s title comes from.
Gardner’s teammates include specialists in math, weapons, and computers, along with their experienced FBI boss.


The story kicks off when DNA from a murder victim matches a serial killer everyone thought was dead. When a second person is killed, the team spots a pattern. The murderer begins leaving special clues and puzzles meant only for Gardner.

Each team member must use their expertise to identify the killer. But there’s a problem – the killer is finding out more about the PAR team members. The big question becomes: can they protect themselves and their loved ones in time?

This was my first book by this author. I requested the book, because I enjoyed the idea of a special FBI team with super smart people having to solve cases nobody else was able to figure out.
For this, I enjoyed the character of Gardner. I thought it was particularly well developped. Besides his brilliant brain, he has issues to relate with others, and is very sensitive, which can lead him to violence when his loved ones are in danger.

And this case definitely needs the smartest team you can get. How can a murder victim be a serial killer who died some years ago? What connects the following victims? And how can the killer always be one step ahead of Gardner?

I liked the complexity and suspense of some scenes, for instance a special scene in marshes.
The environment is very well captured, especially in Florida and Texas. I felt there, with the creepiness, in the dark.

But as a whole, the book didn’t totally work for me.
I actually found it too complex, and with too many characters, too many back stories and layers, and sometimes last minute revelations that seemed awkward.
It takes a long time before things start really going somewhere. The book could have been shorter and more punchy.

McMahon crafts a compelling narrative that seamlessly blends intricate puzzle-solving with intense action sequences. The strength of the novel lies in its well-developed characters, each bringing unique skills and perspectives to the team. Gardner Camden, in particular, is portrayed as a complex protagonist—brilliant yet socially awkward, making him both relatable and intriguing. The dynamic between Gardner and his team members adds depth to the story, highlighting themes of collaboration and trust.

The plot is fast-paced and filled with twists, keeping readers on the edge of their seats. McMahon's writing is sharp and engaging, with a narrative that balances suspense with character development. While the premise of a serial killer targeting other killers is not entirely novel, McMahon's execution offers a fresh perspective, making the story feel both original and captivating.

Interesting plot and the book kept my interest. However the ending didn’t do it for me and sometimes that makes a whole book for me.

Rating: 4 stars

I love procedural/detective books, and this one felt like a deep dive on the detective / puzzle decoder profession. This book had a lot of twist and turns, and every character was so complex, it made for an interesting read! This is the first book in a series, and I look forward to picking up the next one!

Thank you Netgalley for this ARC of Head Cases by John McMahon. This was a fast-paced, exciting read. This story follows FBI agent Camden, who works in a dept. called Patterns and Recognition (PAR). When a serial who was thought to be dead turns up as a victim, Camden lands the case. This is definitely a story with some good twists. A little further character development, especially regarding dialogue could be better. Overall I do recommend this book, if you enjoy thrillers.

Such a great start to what promises to be a great series. I was totally riveted to this book. This new character is so interesting and how he figures it out is great! I need to read more by this author. I see book 2 already has a name. Bring it one!!

Couldn’t get into this book. I struggled staying interested and connecting with the characters. I loved the cover art for this book.

John McMahon has a winner with Head Cases, the first book in the PAR Unit series. Filled with unusual characters hunting down a murderer seeking his own brand of justice, the FBl's Patterns and Recognition (PAR) unit is generally tasked with solving cold cases.
The team consists of five misfit agents led by Frank Roberts, but the main character is Special Agent Gardner Camden.
A serial killer from one of Gardner's solved cases, thought to be dead for more than a decade, is found murdered. Soon, there's another similar case. The killer has left clues and riddles, but can the team solve them?
Gardner is intelligent, confident, all business, and has an eidetic memory. He thinks in terms of layers and patterns, avoids friendships with most, and can come across as arrogant. He has an affinity for riddles, puzzles, and codes. I enjoyed how the author brought to life both the personal and professional lives of Gardner.
As readers learn his background, it provides insight into his thoughts, behaviors, and actions. It was fascinating to see how Gardner's mind worked to solve the various puzzles.
Frank is a career agent and the other members include a mathematician, a sniper and weapons expert, and a computer analytics specialist. The secondary and tertiary characters are reasonably well-drawn for the first book in the series and I would expect the repeat characters to gain more depth as the series progresses.
It was also delightful to see how this team of supposed misfits worked so well together.
I was immediately intrigued by the storyline and the complexities in the plot. It kept me captivated throughout the novel. It was fascinating to see the story unfold.
Full of suspense, this thriller looks at justice through the eyes of Gardner, but readers also get a feel for the antagonist and the vengeance that is sought.
The conflicts move the story through some twists and turns as the story gradually builds momentum and finishes with some surprises and an action-packed finish. The novel also illuminated the politics that can go on behind the scene for agents that don't fit the traditional mold.
Overall, this was a compelling and dynamic story with excellent characterization, good pacing, and a great plot that includes solid procedural details. I can't wait to read the next book in the series which is expected in 2026. Those who enjoy crime thrillers and FBI investigations with extraordinary characters as well as those who enjoy solving puzzles will likely enjoy this novel.
Thank you to Minotaur Books and the author for providing me with an ARC for my honest opinion!

Head Cases by John McMahon is an in depth and fascinating FBI thriller that took me surprise by how it pulled me into the story.

I must say, this book took me a hot minute to get into because I wasn’t immediately sure how I felt about it and had to take a step back from it as a result. However, this said, once I gave it another chance, I was surprised by how deeply it grabbed my attention. I think initially I struggled with investment into Gardner as a character because he comes across as so clinical and removed from people and it was hard to connect with him as a result. Once I got passed this and used to his personality I became so enmeshed in the story and the cat and mouse chase between the FBI and a serial killer killing, well, serial killers, that I flew through the pages and was surprised I sat on this book for so long.

Gardner is an incredibly intelligent agent and seeing him use his intelligence becomes something of an entrancing experience as he puts together connections other people aren’t prone to seeing. He also reveals himself to be a somewhat flawed individual who still manages to care about the people who really matter to him. He possesses some social limitations as someone who doesn’t quite fully understand people and social interactions despite his incredible intelligence, and seeing his interactions with the people who are important in his life really humanizes his character.

The case itself is so interesting to watch unfold, and the intelligence of the clues that unravel it bit by bit were so fascinating. On top of this, there are the high stakes of trying to catch a killer before they kill again, and the threat to Gardner as he gets closer to finding out who the serial killer is.

I really ended up enjoying Head Cases in the end, and it left me curious to read more of the series as it comes out. I’m thoroughly invested now.

I received this book as an ARC from NetGalley.

This novel centers around a group of unusual agents in the FBI. They make up the PAR group - Patterns and Recognition. They use their skills to solve difficult cases. Generally working in the background, they are called into the field to investigate a series of murders.

I enjoyed following the techniques this group used to try to find the killers. This is listed as PAR Unit, #1 and I look forward to future episodes.

The book has a concept that I really enjoy, with interesting characters, action and an inside look into an investigation. I really liked, how the story didn't drag, it went right into what it was about. And I really look forward to reading more books with these characters!

I don’t know how I missed this but I could kick myself! What a book!

The PAR unit is such a unique team and a huge reason why I flew through this book – their extraordinary abilities to perceive indistinct patterns and puzzles is a thing of beauty but has unfortunately earned them the nickname ‘Head Cases’ and puts the unit in peril of being shut down. That is, until a case comes along that could put them at the top.

When a vigilante serial killer targets serial killers – I know, shocker! The team uses their particular set of skills to narrow down the suspect.
I co-read this while listening and Will Damron just slayed the narration! Bravo and well done, Will!

I’m looking forward to more in this series!