Paladin’s Grace by T. Kingfisher

Stephen’s god died on the longest day of the year… Three years later, Stephen is a broken paladin, living only for the chance to be useful before he dies. But all that changes when he encounters a fugitive named Grace in an alley and witnesses an assassination attempt gone wrong. Now the pair must navigate a web of treachery, beset on all sides by spies and poisoners, while a cryptic killer stalks one step behind