Judith Tarr is a master of historical fantasy. As she has done many times before, she takes historically accurate, at least to the best of my limited knowledge, setting and characters, and reinterprets events based on magic being a real force. With the sole exception of her collaboration with Harry Turtledove, Household Gods, she has never to my knowledge written a bad book, and she hasn't broken her string with this one.
Devil's Bargain tells the story of the Third Crusade as it might have happened if there were good magicians, and also evil ones who bargained with dark powers, on both sides of the conflict. It becomes a good sword and sorcery story, with significant romance elements. It is interesting in its depiction of magic, especially eastern magic associated with the Islamic culture. There are battles magical and mundane, intrigue, betrayal, jealousy, reconciliation, love, and a cast of characters that seem very real even after putting the book down.
This is maybe not quite as good as some of Tarr's other books, but it certainly doesn't miss by much. 9 out of 10.