Montparnasse and its caf life, the shabby working-class area of the place de la Contrescarpe and the Pantheon, the small restaurants and caf s along the Seine, and the Right Bank world of the well-to-do . . . for American writers self-exiled to Paris during the 1920s and 1930s, the French capital represented what their homeland could not: a milieu that, through the freedom of thought and action it permitted and the richness of life it offered,...