Dan Wells "Mr. Monster" is a wonderful follow-up to the first book in the John Cleaver series, "I Am Not A Serial Killer." It truly surprised me how engaging this book was, even in light of its tough subject matter, and it's an ever present reminder that the scariest adversary one may face doesn't lie outside of ourselves, but within. The writing is smart, the analysis is spot on, the terror is very real, and in all aspects, I can honestly say I was more freaked out about this book than the first because it deals with things that are scary on the psyche, rather than on gore.In this book, John is faced with the ever present temptation of becoming a serial killer. Following the events of the previous book, he's killed a supernatural demon in Clayton County, thereby releasing an inner evil within half of him which he calls "Mr. Monster." But another serial killer, possibly like the one John killed in the previous book, is on the loose in town, and John is both intrigued and determined to find him.But the book doesn't simply focus on the conflict revolving around the serial killer and John's inner demon. It also deals with him trying to fit in as a normal teenager (going on dates, interacting with his classmates and trying to find common ground), and deal with situations in his family that teem on the edge of turning him into the monster he wishes not to become. It's a book that may shock some readers who read alongside John's deeply disturbing thoughts. However, watching him in the progression of events makes a character worth reading and fighting for, especially seeing how he grapples with the demon inside him.There were some moments I can say I had to suspend disbelief (I don't think a kid John's age with only a permit can drive without his parents unless he gets a restricted license which enables him to drive to school or work only, but even then, it may be a state-by-state thing), and it's a difficult book to recommend for certain audiences because the content may shock readers, but I think it's one that's well worth giving the time to.