A House-Boat on the Styx

The premise of the book is that everyone who's ever died (up to the time of its publication) has gone to Styx, the river that circles the underworld. The book begins with the ferryman Charon being startled & annoyed by the arrival of a houseboat on the Styx. At first afraid that the boat will put him out of business, he later finds out that he is actually to be appointed its janitor. What follows ...