In spite of the sobering topics that it treats, the book isn't really about those things. At its heart, it's an absolutely beautifully written story about love (friendship, romantic, parental), finding one's place/"belonging," rules (of all kinds--explicit, unspoken, laws, etc.), and who gets to make what kinds of decisions for who, based on what, and why. Beautiful, meaningful, and tragically sweet in a thousand different ways.
Seriously. I put this one up there with Uncle Tom's Cabin and the like--everyone should have to read it and that's just all there is to it.