Thello may While they may not have a Pulitzer or Booker prize, the Sidewise Alternate History Awards deserve respect. Regardless, the fiction genre is rapidly growing with works of astonishing quality and originality. The latest Sidewise long-form winner is Francis Spufford’s “Cahokia Jazz.” Set in the 1920s, the noir thriller imagines an America where the indigenous population was not nearly wiped out by smallpox. Other winners of the 29-year-old prize include Laurent Binet’s “Civilizations,” which imagines the Incas invading Europe in 1531, 39 years after Christopher Columbus discovered America. Changing history is certainly about as much fun as a novelist can have: losers become winners and everything remains unchanged. What if General Lee had won at Gettysburg? What if Napoleon had seen off Wellington and Blücher at Waterloo? Nazis are over-represented on alternative history bookshelves, as they are in other sections of most libraries. “Conspiracy Against America” with For example, Philip Roth installs suspected Nazi sympathizer Charles Lindbergh in the White House. John F. Kennedy, who skipped his visit to Dallas or perhaps fell victim to the mob/Cubans/Russians/Lyndon Johnson, is not far behind. The world of imagined pasts is rich and potentially endless, as this selection of the best alternative history novels shows.