A House-Boat on the Styx

The premise of the book is that everyone who has ever died (up to the time in which the book is set, which seems to be about the time of its publication) has gone to Styx, the river that circles the underworld.

The book begins with Charon, ferryman of the Styx being startled—and 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 the boat's janitor.

-- From Wikipedia