Fans of Criminal Minds, Law and Order, and FBI police procedurals pay attention!! This book, Head Cases, is going to be exactly what you love but in book form. I could not get enough of this one, and envisioned it playing out in my head just like a tv episode.

I love the cast of characters, and the premise is very exciting. New favorite series? I think so!

"Head Cases" is the pejorative assigned to the Patterns and Recognition (PAR) Unit, a small group within the FBI staffed by agents with unusual approaches to analyzing cases. These agents do not typically go into the field; rather, they analyze information that others have gathered, then apply their unique skills to produce leads.

Though not named as such, it's clear that the agents are all neurodivergent, and their careers have stalled within the bureau. They're seen as misfits and weirdos by the director and his deputy.

One such agent is Gardner Camden who is skilled at solving puzzles, and does not fully understand how to interact with people, causing upset feelings generally when he does. He harmed his career years earlier when he called the authorities on his wife, who was the daughter of his mentor within the FBI, when Garnder discovered she was involved in financial crimes at her job. He has a young daughter, Camila, who now lives with his mother-in-law, who tolerates him unhappily.

The PAR unit is run by Frank Roberts, a quiet, thoughtful man. Members are Gardner, recent arrival Cassie Pardo, who is good at math and is detail-oriented; there was an incident with Cassie's previous boss, which propelled her into the unit. Joanne Harris, known as "Shooter" is a weapons expert, and ended up in PAR after disagreeing quite publicly with a superior. The newest addition to the group is Richie, who actually chose to join the unit, and whose personnel file is sealed, which seems suspicious to Gardner.

The novel opens with Gardner and Cassie arrive at a suspicious death. Gardner realizes, once they start investigating, that the dead man is a serial killer thought to be dead already. Frank has Gardner lead the case.

Then, another serial killer is found dead. Gardner realizes that yet another serial killer is targeting accused serial killers when strange clues are found on the dead men.

It becomes clear that their suspect is someone who enjoys puzzles, and this person is leaving these behind for the PAR unit to decipher. This person also contacts Gardner, taunting the agent, implying that they are playing a game together. Gardner has PAR pull up old cases and go through them using the agents' skills with patterns to find any leads, even while the killer begins threatening Gardner's family.

The pace is fast and this story is smartly written. The characters are intriguing, and I enjoyed the interactions of the PAR agents. Gardner is sympathetic, and though he struggles in his interactions, I loved his relationship with his young daughter Camila.

I sure hope we get more cases soon for PAR to solve -- I really liked this book.

Thank you to Netgalley and to St. Martin's Press for this ARC in exchange for my review.

A suspenseful, cat and mouse thriller with a Criminal Minds vibe. The writing pulled me into this intriguing story and fascinating characters. Most definitely will pickup future installments.

Thank you NetGalley and St. Martin’s Press for the ARC in exchange for an honest review.

Thank you to St. Martin’s and NetGalley for this ARC. I enjoy legal thrillers and police procedural so I had to request this book! This is my first by John McMahon and I was happy to read it! The novel did throw an awful lot of information at tot but I found it navigable and not overwhelming. I found myself drawn in from the start and the fast pace made it an enjoyable read. I can see this turned into a crime show and I hope the author follows through were these characters for future installments.

If you know me, you know I love my police procedurals and I’ve been craving a strong detective/police procedural lately. I’ve been looking for something to tie me over until the next Karin Slaughter book comes out, and I think I found a new author to watch for.

The first in a new series, Head Cases follows FBI Agent Gardner Camden and his team the Patterns and Recognition (PAR) Unit as they case a serial killer killing…serial killers. The first victim – one of Camden’s cases from years ago that the FBI thought had died. Can they catch the killer before the case become too personal?

Slow Horses meets Criminal Minds. Plenty of action and a good balance of characters. Camden has neurodivergent tendencies, and I felt that McMahon did a wonderful job of giving him growth but keeping him realistic. I primarily listened to the audiobook and Will Damron was an amazing narrator for Camden. I definitely loved the way this series started, and I can’t wait for the PAR #2. Going to have to dive into McMahon’s P.T. Marsh series next!



Head Cases is out now. Huge thank you to Minotaur Books & Macmillan Audio for my advanced copy in exchange for my honest opinion. If you liked this review, please let me know either by commenting below or by visiting my:
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✨ The Vibes ✨
If Criminal Minds was a dark comedy

📖 Read if…
✨ You’re still waiting for a new season of Mindhunter
✨ You enjoy the band of misfits energy of Guardians of the Galaxy
✨ You don’t mind dark humor

To be fully transparent I didn’t really know what to expect when picking up Head Cases. The cover didn’t give much away and the summary read like your standard thriller. But as soon as I finished the first chapter, I knew this book was something special.

Head Cases throws you right in the middle of the action, opening with Agent Gardner Camden and his partner investigating the highly suspicious death of a serial killer who allegedly died years ago and things get even weirder when it appears that this new killer is targeting Agent Camden himself. That’s when the Patterns and Recognition (PAR) unit steps in, a group of quirky agents that are brought in to investigate the cases no one can solve.

It takes a minute to get accustomed to the tone and structure of Head Cases. Agent Camden narrates the story and often jumps between his thoughts on the case, reflections on previous cases, and concerns about his young daughter, but once you adjust to this stream of consciousness, the book is a lot of fun. The mystery is dark and complex, full of puzzles that will have even seasoned readers of the genre questioning their theories. And the humor! It feels weird to say a book as intense as this one is funny, but it really is. McMahon does a great job of incorporating dark humor in a way that never makes light of the more serious elements of the story.

Based on Goodreads, I think there is a sequel in the works, and I would gladly read more about this ragtag group of investigators. Head Cases is out now. Thanks to Minotaur and NetGalley for the eARC in exchange for an honest review.

John McMahon has entered into my auto read author list with Head Cases. In this one we follow a specialized unit of the FBI as they try to catch a serial killer enacting his own justice upon other killers. The pacing was creeping and slowly burning toward the end, adding just enough tension to keep me up late into the night to finish this book. I really enjoyed all of the characters. Their personalities worked together so well and reminded me of procedural TV shows that I always loved. I cannot wait to read the next book in this series.

Flawed but likeable characters and an interesting storyline made this a good start to a new series. I wasn’t sure I’d like it but I’ll definitely read the next one.

This book was a little rough to start with. I wasn't super engaged until about 40% into the book, but then, I couldn't put it down.

It's not meant for the squeamish, as a serial murder mystery, there are some gory descriptions. This book was intelligently written book that focuses on a quirky unit of the FBI full of wounded and gifted individuals and how they work through an unpredictable case. I can often kind of figure out murder mysteries pretty easily, but this was well written and developed so I couldn't predict until the very end.

A specialty group of FBI agents that are put together for their unique talents to create a rag-tag team who focuses on the patterns of crimes. Garnder Camden is the leader of this group and takes his team through some brutal killings that hit close to home. A great read that I highly recommend!

Head Cases has gotten quite a bit of buzz since it came out in January. It was a great start to a new crime fiction series.

The main character, Gardner Camden, is neurodivergent. He recognizes that he doesn't interact with people like most others do but in the course of the investigation, he makes the effort. A member of the special PAR unit he doesn't usually have to interact with anyone but his team. However, the case that has come across his desk is one he worked on before he was moved to the PAR unit. He was the lead investigator then so he is automatically the lead investigator again.

This is a mix of police procedural and psychological suspense. The PAR team kind of reminded me of the television show Criminal Minds. Every agent in PAR was sent to that unit for a reason - none of them chose it. But they are good at what they do.

I'm definitely looking forward to the next book in this series.

My review will be published at Girl Who Reads on Tuesday - https://www.girl-who-reads.com/2025/03/head-cases-by-john-mcmahon-review.html

Once you break the seal of "Head Cases", you will not stop reading until the case is closed. The question is, who will be left to close it? Within the Patterns and Recognition (PAR) unit, FBI Agent Gardner Camden leads a diverse troupe of investigators, as brilliant as they are quirky. PAR is both a secret weapon and a last resort for tackling unsolvable cases.
DNA at a murder scene determined to be from a known serial killer thought to be dead for years quickly lands the case on Camden's desk. More victims are piling up and the killer is leaving taunting clues daring the team to catch him if they can, Camden and team are literally reaching to get ahead of the killer, but there is trouble within. You see, you don't land in PAR because you are among the best and brightest. You are sent there when you have royally screwed up, but the FBI is not quite prepared to cut ties. Trust within the team hinders the investigation. A trust that puts their lives and the life of Camden's young daughter at stake, He cannot get this wrong.
Characters are well developed, human, flawed. McMahon skillfully weaves layers of intrigue beyond the case itself, adding depth without ever making it feel distracting or unnecessary. This is the first in a series that I cannot wait to continue reading!

My thanks to NetGalley and St. Martin’s Press – Minotaur Books for the ARC of this novel in exchange for my honest opinion.

Head Cases by John McMahon is a gripping, fast-paced crime thriller that pulls readers into a dark and gritty world of suspense. The novel follows a detective as he navigates a series of complex, twisted cases that challenge both his moral boundaries and his investigative skills. McMahon’s writing is sharp and immersive, with well-crafted characters and a tightly woven plot that keeps you on the edge of your seat.

The pacing is excellent, and the book does a great job of balancing action with moments of introspection, adding depth to the characters. While the twists are engaging, there are moments where the story can feel a bit predictable, but the overall intensity and compelling narrative make up for it.

Overall, Head Cases is an enjoyable read for fans of crime fiction, offering a solid 4-star experience with its dark themes, strong character development, and suspenseful storyline.

Good start to a series with some rough edges. Takes time to take off but a decent police procedural noentheless. Looking forward to the next some with the hope that the pacing gets a bit polished

Fans of Criminal Minds are going to love this one!

Let me lay the groundwork…
🔎 Misfit group of FBI agents
🔎 Fast paced setting
🔎 Killer who is hunting other killers

Agent Gardner Camden may be in charge of this case, but prepare yourself to adore the members of his team as well! Each of them has their own unique quirks that make them essential for solving this case.

There is an overarching sense of urgency that makes the pacing of the story fly by as our team chases their killer. The case, the motive, the killer, the people…all chef’s kiss!

This is the start of a series, but this book feels whole and complete by itself. I look forward to another installment with the PAR Unit and what intense case they might be working on next.

A great start to a new series. Started a little slow but then took off running! Highly entertaining for anyone who loves FBI profiler mysteries or True Crime.

This book was definitely one of my favorites so far this year. I love that the characters are all misfits in one way or another and have all epically messed up somewhere along the line, but all have their own unique skills that somehow manage to mesh together to carry a book that I couldn't put down. The plot was fast paced but nothing about it seemed rushed. The characters were fun and very multidimensional. I cannot wait for there to be more to this series and am very much looking forward to continuing it in the future!

This was a good debut! If you love police procedurals that follow a serial killer, then give this one a try. It is a bit slow paced at first, and while less dark than I expected, I enjoyed the storyline. I found Camden's character well fleshed out and his methods intriguing. I do wish we had a bit more background on the other members of the PAR unit (patterns and recognition) but maybe we will get more in the sequel!

Rating: 3.5/5

Thank you to St-Martin's Press, Minotaur books and NetGalley for the ARC. All opinions are my own.

This book gives TV show vibes—think Law & Order or Criminal Minds. The book centers around PAR (Patterns and Recognition), a unit of the FBI, composed of highly skilled individuals that are a bit quirkier than typical agents who are able to think outside the box. I’m glad to hear it’s a series because we get to know each member of the team during Headcase and I can’t wait for their characters to develop more.

In Headcase, Agent Gardner Camden responds to a call regarding a murder victim believed to be a serial killer. The way he died was unconventional and there are many unique clues that make PAR perfect for the case. As PAR begins their work on this murder, another serial killer comes up murdered and the patterns continue…the only problem is, it seems like the suspect might be inside the house (figuratively).

Camden has a job to get ahead of this new serial killer before those he cares about, or even himself, may fall into the killer’s hand as their next victim.

This book was engaging and Camden’s character was well fleshed out. I loved his unique thought process that the writing detailed perfectly. The story was gripping and I seriously was trying to put all the pieces together to figure out the killer myself (spoiler, I did not).

Thank you to Minotaur Books, St. Martin’s Press and NetGalley for the ARC.

Readers who love cat and mouse thrillers, serial killer profiling, and police procedural will want to pick up Head Cases by John McMahon. I found the writing captivating and increasingly claustrophobic as the showdown between a FBI agent in the Patterns and Recognitions Unit is attempting to identify and take down a killer. A mystery with cryptic clues, taunts, and increasing danger, this was a superior thriller!