Divergent
The first book of a Trilogy.
Summary
Beatrice Prior lives in a future version of Chicago where there are five distinct factions. Each faction thinks one virtue is best: Dauntless think bravery is keen, Erudite love knowledge, Abnegation is pro-self-sacrifice, Amity hearts friendship, and Candor is into telling it like it is. Beatrice grew up in an Abnegation family. But when she turns 16, she decides to join Dauntless, partly because they're cool (tattoos, piercing, leather jackets); partly because she doesn't feel selfless enough to be a good Abnegation; and partly because her test result showed that she was Divergent, meaning she doesn't really fit in with any one faction.
But joining Dauntless isn't just about showing up and saying "take me." All the initiates have to train and compete to get into the faction. Along the way, Beatrice takes a new nickname, Tris, and meets a lot of new people. There are new friends like Al, Will, and Christina; new enemies like Peter and his evil minions; and new teachers, like the scary Eric and Four. Tris has to compete to get into Dauntless, all while hiding that she's really Divergent.
Then, Tris figures out that the Erudite faction wants to overthrow the Abnegation government. And they're going to do so by mind-controlling the Dauntless army. But Tris doesn't get brainwashed (because she's Divergent), so she destroys their plan, and rescues everyone. Except for her mom and dad, who die to help her.
Beatrice "Tris" Prior
Tobias "Four" Eaton
Caleb Prior
Theme: Identity
A big part of identity here is figuring out where you fit in; for Tris that means that no matter how hard she tries, she's never going to fit into her world.