The Doorverse Chronicles

John Gilliam, the Faceless Man, is one of the premier assassins in the world.  His skills are legendary, and he's never failed in a mission.  When a job goes wrong, though, he discovers that there's an entire universe beyond what he knows, one where magic and monsters exist and his skills and talents are frail shadows of the powers that be: the Doorverse. Now, John has a new job.  As an Inquisitor, he's tasked with traveling the Doorverse and righting the balance on the worlds he finds.  Each world is unique, and John has to learn how to survive anew every time he passes through another door.  Led by his AI guide, Sara, he'll have to become more than a killer-for-hire, and more than just a human if he wants to survive the Doorverse!