Gemma, by Meg Tilly

This is a truly disturbing and graphic book about child sexual abuse. It's pretty horrifying, and also compelling. Mainly told from the child's perspective, but with glimpses of the abusers' attitudes as well. And it does have a "happy" ending, or at least as happy as one can expect. It reads hard and fast; I read it in one sitting. If that kind of stuff freaks you out, or stays with you for weeks, I would skip this one.