BOOK REVIEW / NOVEL : Wild, Witty Yarn About the Death of God : TOWING JEHOVAH <i> by James Morrow</i> ; Harcourt Brace $23.95, 327 pages

God is dead.

People used to say that a lot in the 1950s. Academic types, French existentialists.

I was just a kid. I didn’t know whether they meant that there had been a God once and he had gone poof! or that he hadn’t ever existed and it was our naive belief in him that had died.

I still don’t. Back then, I wasn’t sure they knew. They seemed to mean it both ways at once, which was logically impossible.

In fiction, necessarily, the idea was less abstract, more corporeal. Philip Wylie, the once-famous author of “A Generation of Vipers,” wrote a story about an angel who fatally crash-lands on Earth like a space shuttle with faulty O-rings. Tom Robbins’ first novel, “Another Roadside Attraction,” had the Catholic Church concealing a 2,000-year-old secret--the unresurrected body of Christ--in the Vatican basement.

Now it’s James Morrow’s turn. In “Towing Jehovah,” the veteran science-fiction writer (“Only Begotten Daughter,” “City of Truth”) has God die and fall into the Atlantic Ocean. The Angel Raphael, wasting away like the rest of the heavenly host of “terminal empathy,” enlists a disgraced supertanker captain, Anthony Van Horne, to tow the two-mile-long corpse to an Arctic tomb before it rots or is eaten by sharks.

The expedition is underwritten by the Holy See, which hopes that salvageable neurons remain flickering in God’s brain. Otherwise, the Church would just as soon pour crude oil over the embarrassing remains and set them afire--hardly what the angels had in mind.

In this satire of Western culture both sacred and profane, Van Horne must contend with more than hurricanes, icebergs and bad dreams. His ship runs aground on an uncharted island. His crew mutinies. The Vatican sends out an armed vessel to intercept him, captained by the stern father who hasn’t spoken to Van Horne in years.

There’s worse. Cassie Fowler, a castaway Van Horne picks up at St. Paul’s Rocks, is a feminist and rationalist. God’s death is no consolation to her; she is horrified to discover that he did exist, and that he was, after all, the white-bearded “God of Western patriarchy.” No less than the Church, she wants to get rid of the corpse.

More happens in “Towing Jehovah” than can be summarized here. Morrow makes it happen with Vonnegutian verve and wit and an enviable expertise in fields ranging from seamanship to junk food to Bob Hope routines to theology. He echoes the Bible, Shakespeare (“The Tempest”), Dostoevski and Cecil B. DeMille. His exploration of “theo-thanatology” touches all the bases:

Does God’s absence give humankind the amoral and terrible freedom that Ivan Karamazov envisaged? Are there really no atheists in foxholes? Can religion continue to flourish without God? Can quarter-pounders with cheese replace communion wafers?

Only twice in this wild yarn do we pause in doubt. The first is when the island, studded with pagan ruins, rises from the sea to intercept the ship. We drift away from both God and Van Horne then; we pass from a semi-realistic world in which one incredible thing has happened into a world in which unbridled magic begins to lose its value.

The second is at the end, when the issues Morrow has raised grumble and subside, like lions too sleepy and overfed to eat the lambs they lie among. This is where he parts company from Vonnegut, whose every book is haunted by the night he spent in Slaughterhouse-5 while the bombs fell overhead on Dresden, and from those postwar existentialists, who were driven to their conclusions--however ambiguous--by genuine horrors. They cared.

What makes this novel so buoyant and, ultimately, a little disappointing, is that Morrow doesn’t care as much.