You certainly meet all kinds of people out on the slopes. The best of this lot is John Updike, who sets his story of an asthmatic father and athletic daughter high up on a wind-chilled expert trail. B.J. Chute recreates the thrill of skiing out of control and gloriously beyond one's abilities; David Judson evokes the practiced pleasures of a well-coached junior sportsman; and Adrian Stoutenberg and Laura Nelson Baker contribute a fictionalized tribute to ""Snowshoe"" Thompson who built 25-pound copies of the cross country skis he remembered from his Norwegian boy-hood to carry mail across the Sierras. Other authors rely more on hobby horses than on skis for locomotion--grouchy or reluctant lovers, a power-mad millionaire, a shell-shocked soldier and a claim-jumping prospector are among the clumsy crowd sloshing about on the beginner's hill.