While France endured one of the darkest hours of its entire history, from the occupation of Paris in June 1940 to the liberation of the city four years later, the French art world displayed an astonishing burst of creativity, an atmosphere of laissez-faire and pluralism that seems at odds with the repressive nature of culture under authoritarian regimes. So reveals Michle Cone in this provocative work on the art of Vichy and occupied France. But,...