In Young Mr. Roosevelt Stanley Weintraub evokes Franklin Delano Roosevelt's political and wartime beginnings. An unpromising patrician playboy appointed assistant secretary of the Navy in 1913, Roosevelt learned quickly and rose to national visibility in World War I. Democratic vice-presidential nominee in 1920, he lost the election but not his ambitions. While his stature was rising, his testy marriage to his cousin Eleanor was fraying amid scandal quietly covered up. Ever indomitable, even polio a year later would not suppress his inevitable ascent.

Against the backdrop of a...