LEADER OF THE BAND by Fay Weldon
Viking; 196 pages; $18.95
Sandra Sorenson, 42, is an astronomer who is quasi famous for having discovered a new planet in the solar system. She appears once a month on late- night British TV to discuss the universe, and has been dubbed "Starlady Sandra" by the tabloids. But recognition does not satisfy her, and neither does her husband Matthew, an ambitious lawyer and tepid bedmate ("What's good enough for missionaries is good enough for me"). So Sandra does what any woman in her fix would do: she runs off with Jack Stubbs, the trumpet...