Another dystopia (what is the fascination with these things?).
In this one, Chicago has been turned into a camp of competing factions -- Abnegation (self-sacrificing), Candor (honest), Erudite (intellectual), Amity (peaceful), and Dauntless (warring). At the age of 16, each child must choose where they want to live. Beatrice, raised in an Abnegation home, has never felt worthy enough to stay and struggles with her decision. She chooses to become Dauntless. The initiation process is far from easy and a bulk of this book is devoted to that difficult process.
However, there are other forces at play and far more serious stakes. The factions are restless and struggling for control. Beatrice (renaming herself as "Tris") has an important role to play. Her rootless feelings are actually a result of her status as an outsider to all of the factions -- a "divergent" one -- a position that she must keep secret. It may well be the key to saving her people but could easily get her killed.
This is a fairly creative set-up. While one could complain about the simplistic nature of carving out such absolute "factions," it's well-implemented. The book itself doesn't break much new ground though. There's the high degree of brutality and violence that has become a trademark of the genre (e.g., Hunger Games or Ship Breaker). There's the appealing but ultimately egocentric idea that adults are worthless for saving the world and that only a team of adolescents can pull it off. In other words, stuff we've seen before. The novel does have some interesting things to say about violence, parents, and fear, but in the end, it's mostly a gorefest. This is seen most clearly in the token romances in the story, which are never allowed to interfere too much with the action. Once the troops fall under mind control (in a sequence lifted shamelessly from the movie I Robot), we just sit back and watch the body count climb. Movie options and the sequel (due in May 2012) are a foregone conclusion.