The River Of The Dancing Gods: Jack L. Chalker

Book I of The Dancing Gods. Life had not been kind to Joe and Marge. Now, according to the stranger who met them on a road that wasn't there, they were due to die in nineteen minutes and eighteen seconds. But the ferryboat that waited to take them across the Sea of Dreams could bring them to a new and perhaps better life. There lay a world where fairies danced by moonlight and sorcery became real. Joe could become a mighty-thewed barbarian warrior. Marge could be beautiful and find her magical self. But there was much more than they realised to this magical land. This was a world where Hell still strove to win its ancient war and demon princes sent men into battles of dark magic. It was a world where Joe and marge must somehow help prevent the coming of Armagdeddon.