If Woody Allen had gone to parochial school, he might have written this book. Hoffman, who attended Catholic schools in Akron and Denver and later wrote for Phyllis Oilier, began the Sister Mary Mummy Stories as a comedy routine in 1968. They found their way into print in the New York Times, women Sports magazine and Catholic Digest, among other places. The heroine, a formidable but prankish nun, dominates Our Lady of the Gulag. Her pupils will be instantly familiar to properly catechized readers: Prissy Mary Margaret Delicate (who swoons if she spills a speck of ink on her uniform) is an example. Hoffman's lapsed-Catholic humor strikes a perfect pitch between schoolboy awe and refreshing irreverence. The book, not yet in stores, can be ordered from Jorgensen Publishing, 1801 Ave. of the Stars, Los Angeles, Calif. 90067 for $6.95.