UP THE SANDBOX by Anne Richardson Roiphe. 155 pages. Simon & Schuster. $4.95.
Walter Mitty is alive and well in the appealing shape of a young matron on Manhattan's Upper West Side. She is Margaret Reynolds, the decidedly sane housewife-heroine of Up the Sandbox, a fresh, beguiling, bittersweet novel that looks into those three old hats: men, marriage, motherhood.
Margaret stands somewhere to the right of Women's Lib but to the left of total fulfillment through old-fashioned marriage. She loves her husband Paul, a college professor who is a scholar of social disorder. She is inordinately proud of the body that brings her...