Genre: Horror
Sub-genre: YA

Read the full, spoiler-free review here.
Let's be totally fair here: I've never been a twelve-year-old boy. I know, it's a sad fact that means I'm missing out on some experiences, but I chose the other route, the one that involved experiencing a year as a twelve-year-old girl (and by "chose" I mean "lacked the Y chromosome"). I suspect my lack of time as a boy means I'm not the target audience for this book, although in spite of the marketing, I'm not sure middle-grade kids are, either. It read to me like a nostalgia book, the sort of thing you pick up to remember what it was like to be that age, to hover precariously between the comforts of childhood and the alluring realm of teenagers. The Monster Variations holds the sort of truths about growing up that can't be recognized until you've already been through it and can look back with a new perspective.
Even more misleading is the labelling of thriller. I've always seen this book categorized under horror and thriller, and even the back copy promises "a thriller's edge" and tells me "beneath the terror and the thrills, there is truth in this haunting tale." It's not about three boys trying to escape death by psycho killer with a truck. In fact, the truck and the danger it represents disappears from the pages almost entirely for 150 of the 245 pages.
I found a lot of important scenes in The Monster Variations I was told about, rather than shown. One of the three boys would be puzzling out the apprehension and confusion that surrounds growing up, and would then reflect on an important conversation, or exchange, or experience, shortening the summary in their hindsight. I wanted to see rather than hear what was going on, to meet Willie's parents before the accident so I could make the comparison myself, to be there when fistfights broke out rather than hear about it afterwards. Occasionally, too, "maybe" would jump a few chapters and become solid fact, and while the amount of time the narration spends in the boys' heads might excuse this, it was jarring to go suddenly from "I think I may have just seen my father's car" to "yes, of course he was definitely there that night."
This being said, the tone of the book did have the promised feel of truth to it. I could easily believe in these boys and their world, in their struggles and triumphs. They felt like twelve-year-olds, and will ring familiar to anyone who's been that age.