Divergent, by Veronica Roth
I am really late to the party with this book--everyone else is already reading the sequel! I put it on hold at the library a while back, and then when I got it I wasn't sure if I really wanted to read it. It turned out to be pretty good though.
Probably everyone already knows the plot of this YA dystopian story. Set in post-apocalyptic Chicago, society is divided into 5 factions based on character traits, all that good stuff. I didn't actually find the set-up to be terribly plausible, but that's OK. I hardly put it down and I had fun reading it in one day.
If you're wondering whether you can give it to your kid, it's pretty violent and most of the people the protagonist cares about are killed before her eyes. While there is a heartening lack of teenage sex, there's some mention of it. I didn't give it to my own almost-teen.
I'm betting this will be the next movie deal, since it seems to be the next in popularity to Hunger Games (probably it's already in the works and I just don't know).