In ''Short Letter, Long Farewell,'' a German playwright is pursued by his wife, an actress, who wants to kill him. They scramble across the United States - Providence, New York, Philadelphia, St. Louis, Tucson, northern Oregon - to California, where they meet the director John Ford, who utters sage advice that enables them to part in peace. The novel is full of vivid snapshots of American characters and scenes, and the idiosyncratic mixture of narrative, interior monologue, natural description and cultural themes and cliches is a brilliant concoction.