Impostors By Scott Westerfeld
Book/Novel Author: Scott Westerfeld
Book/Novel Title: Impostors
Frey is Rafi's twin sister-and her body double. Their powerful father has many enemies, and the world has grown dangerous as the old order falls apart. So while Rafi was raised to be the perfect daughter, Frey has been taught to kill. Her only purpose is to protect her sister, to sacrifice herself for Rafi if she must.
When her father sends Frey in Rafi's place as collateral in a precarious deal, she becomes the perfect impostor. But Col, the son of a rival leader, is getting close enough to spot the killer inside her . . . .