There is a fifth-dimensional version of our world in which Lincoln was kidnapped from a box at Ford's Theater and never seen again. In that world there is an empty tomb in Springfield."
Thus runs a typical passage from this enjoyable but confusing historical novel crossed with a science fiction time-travel saga. Gore Vidal's protagonist, called only T, is a 16-year-old Washington prep-school student and math prodigy when he is summoned to the Smithsonian in 1939. He arrives to find a complex, never very clearly explained array of historical tableaux come to life, mingled with normal humans (including such characters as Charles Lindbergh, Robert Oppenheimer and Eleanor Roosevelt, with Albert Einstein, Douglas MacArthur and Ethel Barrymore performing cameo roles).
Part of their wide-ranging mission involves going back in time to prevent World War II by eliminating Woodrow Wilson's presidency. T is helped in this aim by a woman who is variously part of an Indian-village exhibit and the first and second wives of Grover Cleveland. In the process he meets a painter-architect named Schickel Grubert, who is the parallel to Hitler in another dimension in which World War II is limited to the Pacific. T also encounters various incarnations of himself, coming and going (and in one case dying).
Vidal spins this yarn glibly. It moves along, densities notwithstanding, and Vidal generally avoids his usual liberal sociopolitical agendas, but the novel ends in a flurry of time-space mumbo-jumbo. Nobody expects Vidal to be a physicist, but he is usually a better storyteller. (Random House, $23)