The Neddiad — Daniel Pinkwater

The old powers try to come back, and the planet is plunged into chaos, and civilization is destroyed, and it gets all violent and evil... the old legends tell that a hero... with the sacred turtle, always ... Los Angeles, California. Neddie Wentworthstein is the guy with the turtle. Sandor Eucalyptus is the guy with the jellybean. Sholmos Bunyip wants the turtle . . . and he'll stop at nothing to get it. This is the story of how Neddie, three good friends, a shaman, a ghost, and a little maneuver known as the French substitution determine the fate of the world.