The Hundred Thousand Kingdoms by N.K. Jamisin (2010) Orbit Books

Yeine is the ennu, the leader of her tribal region of Darr.  They are considered barbarians.  Her mother, though, was the heir of the man who rules the world.  But they were estranged, and her mother has died.  Yeine is called to her grandfather’s city where he informs her that she is to be named one of three heirs to his seat.  She does not like the Sky city or the people of that land, though she is a half-blood of the same people.  These people, the Aerimeri rule with the weapons they made of gods when the gods were enslaved to them.  Yeine discovers that she has been named an heir so that she can be sacrificed in the succession ritual.  But she also befriends the enslaved gods and discovers that one of the original three gods was killed, but a part of her soul was left behind.  In a bargain to save her father, her mother agreed to let them put the last remnants of the goddess’s soul into her baby, Yeine.