Forbidden to rejoin the Golden Horde for fear of contamination, the party disperses and Bold, an aging campaigner, flees through a desolate landscape that makes clear that the population of Europe has been almost wholly wiped out. Kim Stanley Robinson's The Years of Rice and Salt (Bantam, 658 pp., $25.95) begins in the Islamic year 783, 1405 by the Christian calendar, with a scouting party of the Mongol conqueror Temur crossing west through the Moravian Gate to discover a land decimated by plague. The four books before us each embody a familiar mode of twentieth-century SF - alternate history, 'future history,' space opera, and the scientist's creation gone berserk - and its authors are in their fifties, seventies, sixties, and forties respectively, which neglects the younger end of the spectrum but does offer a broad-range look at a genre that boomed with the Boomers (and is now being shouldered aside by various flavors of Fantasy). 'No science fiction novel published at the end of a century of science fiction could stand alone,' as one of the authors reviewed this month observes in an afterword, explaining the pressure of history that weighs on every attempt to sketch the future. New forms of representing the new are not common under the sun, and science fiction (always a more conservative genre than it admits to being) almost never makes a radical break with its past traditions. Looking it over, I think I managed to say some worthwhile things, though I would now put more emphasis on the virtues of Schild's Ladder (whose neat parts still linger in memory). I remember that it had been cut on its original appearance, with the final book omitted. Le Guin, Appleseed by John Clute, and Schild's Ladder by Greg Egan. It considers The Years of Rice and Salt by Kim Stanley Robinson, The Birthday of the World by Ursula K. I came across the file of this science fiction review column, written in April 2002 for the Washington Post Book World.