Is apocalyptic literature set to 20-year cycles? In the late Fifties, we had On the Beach and A Canticle for Leibowitz; and now, in the past few months--one doom book after another. Macauley's version is a skillful one that suggests our downfall will come from a race war and black revolution that catches fire in the 1980s, in which all blacks are ultimately killed; and the whites who remain seem to disconsolately let go of the skills and tools of civilization--they slink off into the bush. So, generations later, America is a barrenness of isolated and primitive settlements, a place of buckskin and reeds. In this setting, Kinkaid, a ""doc,"" a ""healer,"" who by accident has found an old Esso road map, goes west in search of the mysterious ""Michigan'"" mentioned on the map. On his way he's sidetracked into assisting a settler named Haven whose grown daughter has been taken prisoner by a band of horsemen known as ""the southrons."" Based in a place called ""New Mefis,"" the ""southrons"" have installed a rudimentary slavelabor economy, and it is Kinkaid's object to release Haven's daughter from its clutches. Macauley writes his adventure scenes with verve; other conventions, though, are pure cornball. Characters discover, as they lamentably always do in this kind of book, objects and situations they can't identify (but we can): ""'Ford,' 'Burger,' 'Wash-o-Mat,' 'Motel'--words unknown to Kinkaid."" With too much dependence on this sort of Planet of the Apes/Twilight Zone cuteness, Macauley's futuristic vision gradually fades in interest and misses real impact; but it's one of the better recent end-of-the-world entries, with the accent on scenic adventure.