I'm disappointed by other comments I see here. It's true that the book suggests one incident of spousal rape. It's presented, however, in an entirely appropriate light: not graphically described, not setting kids up for emotional trauma, not instilling negative sexual morals in any way. Yes, the presence of rape is a serious aspect of the book, and parents shouldn't just toss it at their kids willy-nilly. Give this book to your children. Let them read it or read it with them. Talk about the difficult aspects of it. Shielding them from the existence of rape won't be any better for their emotional health than letting them read about it.
That said, it's absolutely true that not every child will be ready to encounter these kinds of issues, and that's up to you as a parent to decide. But in general, with parental support, this book should be suitable for preteens.
And, in fact, not just suitable, but with a high potential for being a wonderful experience.