Divergent

Divergent by Veronica Roth p. 496

In this dystopian Chicago, there are five factions: Candor (the honest), Abnegation (the selfless), Dauntless (the brave), Amity (the peaceful), and Erudite (the intelligent). You are born into a faction but you can choose to switch factions on Choosing Day (when you're sixteen). When you choose your faction, you have to go through initiation before you're allowed to be a member of the faction (even if you're from that faction). 
I don't want to give anything away in case someone wants to read it. It was a good book that got better the more you read. I would definitely recommend it to teens and adults.