So, it's nearly impossible to review a book like this without spoilers. I'll do the best to keep spoilers vague, though, because I think this is a really fun and satisfying book. and would prefer people pick it up knowing only what the book description says.
I AM NOT A SERIAL KILLER is not exactly a serial killer book and yet it is.
(This as spoilery as I get:
More importantly, it's not exactly a book that hinges on the "WHOH!" moment, because that moment comes about 100 pages into the novel.So, it's not a twist ending. It's not miscategorized, and yet I can see people getting on board because they like the idea of a sociopathic narrator fighting the urge to kill.
But, let's be honest, the author knows you can't write 200+ pages about a teenager trying NOT to kill. it would not satisfy. it might be a decent enough literary exploration of murderous urges, but even CRIME & PUNISHMENT has the murder and then the guilt. (oh, the guilt.) So, to withhold murder from a straightfoward book about a sociopathic teenager would be a failure.
Thus, the plot of I AM NOT A SERIAL KILLER. it's beyond the easy "just make the victims worthy of being killed" (ie, the Dexter plot).)
While the ending does hinge a bit too much on setup for the next book (this is part 1 of 3), I found the story engaging, fast paced, and easy to fall into. If you're the kind of person that gets upset about believability and accuracy, this book probably won't work for you. But if you're the kind of person that sets aside issues with "Would that really be how a therapist acts" or "This kid is SO not a sociopath!" or "That's not how Dexter would do it!" then you will ENJOY this book. Which is what matters.