IMAGINE A GREAT WHITE LIGHT by Sheila Schwartz (Pushcart Press: $18.95; 287 pp.). These short stories won Pushcart's ninth annual editor's book award for "overlooked manuscripts of enduring literary value." It's a jolly collection--full of irony appropriate to the award and heavy with implications. The title story concerns a woman who has cancer but outlives her son; she is left with an impatient daughter-in-law who is not at all pleased to be the widow of a suicide. It sounds awful, but the writer has the gift of making her most annoying characters sympathetic. Another story involves a young wife who pretends to have a life after her husband goes off to work. When he packs a suitcase, possibly in preparation for leaving her, she pretends to be asleep: If she doesn't notice, maybe it won't be real. Then there's the jealous daughter whose father loved the other sister better. Although the story never states it, there is the ominous possibility that the envied sister paid dearly for the favor. Another story depicts a Jewish summer camp through the eyes of a large 13-year-old girl who is infatuated with one of the teachers. When the camp clown disappears, the girl's imagination takes over completely. These stories are complex, never superficial, and they linger in the mind like interesting strangers.