The page before the title page: NOTE: THIS IS NOT A BOOK FOR CHILDREN. And she means that. One of the greatest aspects of Anderson's writing style is her unflinching plot lines and her massively flawed characters. The first scene describes Tyler getting an erection from (female) tennis players grinding up and down "and moaning. Did i mention they were moaning yet?" to quote from the book. The thirteen utterly perplexes me. The climax of the book (moderate spoilers) is about a girl getting so far drunk out of her mind that she passes out, a guy takes naked pictures of her and puts them on the web; ultimately Tyler is blamed and threatened with verbal police brutality and his father nearly forces him to go to military school. I don't know how that's not graphic, I mean, various references to pornography, uncontrollable hate for everyone and himself, strong language...but when most readers are thirteen they (by they I meant I) were reading Artemis Fowl. This book deals with conflicting moralities and inherent bad behaviors and qualities that neither the parents or children wish they had. While it is red, the number thirteen shouldn't even be on there. I would give it a yellow for extremely mature 15 year olds.