Before reading this book, you need to prepare yourself:
It's going to be disturbing.
It's going to turn your stomach to knots.
It's going to make you very, very angry.
I won't go into the plot since several reviews and the book description already do that. I will say that to me, this book reveals the ugliest possible sides of human behavior, the worst being when good people do NOTHING to help. The worst part about it is, this book is based on a true story.
Even the author is disgusted by what happened, according to his note at the back of the book. READ AT YOUR OWN RISK!