While this book is partially a family story and partially a mystery, the message and the main plot center around the friendship between two 13 (?) year old boys. The book emphasizes the power of love and the necessity of trust in friendship, and shows the way that secrets can tear people apart.
This book has very strong, positive themes (love, friendship, the destructive force of secrets and shame, familial bonds, the process of growing up, and above all, the power of friendship) and I would strongly recommend it for anyone 13 and up.
Parents should know that it does deal with somewhat mature issues at times, but trust me, it is not even close to being half as bad as the majority of the stuff in the media these days, and it deals with them in a mature, non-invasive way that I think is very accessible for young adults.
Yes, a part of this book deals with a kid experiencing sexual feelings for the first time, but that is NOT the main point at all and the book does not treat it like a good thing. In fact, it makes it very, very clear that the adult behaved wrong and the boy was not to blame. In an age where the media focuses on men abusing young girls, it's good to have a book that isn't afraid to address the difficult truth that it can happen the other way around (a woman abusing a young boy.) Also, this part of the book is a very brief part--the vast majority of the book contains no mention of sex, and it is never portrayed as 'cool' or 'fun.'
But, again, that is NOT the point of the book.
I first read the book when I was about eleven, and I didn't even understand what happened in the infamous 'scene,' but I loved the book regardless--my point being, I came away from it with a positive message (the power of love) and not grossed out and/or corrupted by what I'd read. When I was old enough to get what had happened, it only enhanced my understanding of the story. I've re-read that book every year since the first reading (I am now 20) and every time reveals something new, deep, and touching. I've never read a book that better captures the beauty, heartache, fun, confusion, and love that are part of any true friendship. Definitely recommend it to any teenagers looking for a compelling story that captures the confusion of adolescence without resorting to copious amounts of drugs, drinking, sex, etc.