Shatter City (Impostors, Book 2) - Scott Westerfeld - Bog

"When the world sees Frey, they think they see her twin sister Rafi. Frey was raised to be Rafi's double, and now she's taken on the role--without anyone else knowing. Her goal? To destroy the forces that created her. But with the world watching and a rebellion rising, Frey is forced into a detour. Suddenly she is stranded on her own in Paz, a city where many of the citizens attempt to regulate their emotions through an interface on their arms. Paz is an easy place to get lost--and also an easy place to lose yourself"--Dust jacket flap.