Matched

Matched by Allie Condie
Matched is about a girl named Cassia who lives in a futuristic society.  This society controls everything it's people do and for all of her life, Cassia has accepted that.  Then, she is Matched (married in a sort of way) with her lifelong friend Xander but for some reason, an unusual new boy named Ky gets tangled in their relationship.  Cassia discovers many things that she has never realized about her seemingly perfect society and now she has to make decisions that will change her life forever.
Also, if you have read this book already, look out for Crossed (already came out) and Reached (coming out soon).