This is the second book in Peter Straub's "Blue Rose" trilogy, but I read it first and didn't find myself having any problems (the first book is Koko, which I am reading now).
Tom Pasmore is the only grandchild in one of the ruling families on a small Caribbean island. Unfortunately, that's not enough to protect him from suffering an accident that nearly kills him. He was an odd child to begin with, but his near-death experience changes him in ways he can't understand. Years later, when he's a teenager, he gets involved with a mysterious neighbor, who points him in the direction of crime-solving. Soon, Tom finds himself investigating a decades-old murder and trying to figure out how it connects to his family and to the richest family on the island, the Redwings. Tom's grandfather sends him to the family's summer compound in Wisconsin, and from there things just get more suspicious...and dangerous.
This was a long book, and it started off a bit slowly. I was about a hundred pages in before I really started to get pulled in. After that, though, I couldn't put it down. The character of Tom is very well-drawn, and the secondary characters are also very well-defined. The plot was twisty, and I didn't figure it all out too far before the conclusion, which is great. I first discovered Peter Straub because of his collaborations with Stephen King, and although they definitely have some similarities, Straub's work is both less supernaturally-based and also less tangential. This book is a straight-up mystery (hence the title) but still quite suspenseful.
On the whole I'd recommend it, but it does take some time to really get into.