I described Nine Princes in Amber to my brother as "Jason Bourne meets The Chronicles of Narnia."
The story follows a man named Corwin who has just survived a near-fatal automobile accident. He cannot remember who he is, but he slowly learns that he is the prince of Amber, the kingdom of the real world. There are shadow worlds and real worlds, or worlds of substance. Princes of Amber can travel and create shadow worlds.
Corwin and his brothers are all rivals for the throne of Amber because of some unknown event that removed their father from power. There's lots of treachery, sword-fighting, world-traveling, and magical twists.
Nine Princes in Amber is the first book in Roger Zelazny's Complete Amber Chronicles, of which there are 10.