It's the tale of Fost Longstrider, a courier, who becomes involved in a fight between two princesses. over the six novels (or two collections) it builds to an apocalytic climax. Characters involve a sadistic prince, lecherous genies, and it's set in an alternate earth. Quite a lot of fun, but the high sexual content does not suggest it for children.
Source · Open Library
Placement
- War of Powers — #1
- contained in The War of Powersomnibus