Historian Lesley M.M. Blume's new book, 'Fallout,' tells the story of John Hersey, the young journalist whose on-the-ground reporting in Hiroshima exposed the world to the devastation of nuclear weapons. "Hersey had seen everything from that point, from combat to concentration camps," Blume says. "But he later said that nothing prepared him for what he saw in Hiroshima."Maureen Corrigan reviews 'Black Bottom Saints,' by Alice Randall.