Most books about Hiroshima, Japan, ask readers to confront the atomic horror of August 6, 1945. Kiyoshi Tanimoto’s Hiroshima, 8:15: The Lost Memoir asks something more difficult: what comes afterward. Although Tanimoto wrote the manuscript in English only a few years after the bombing and sent it to the writer John Hersey, it remained buried among Hersey’s papers for decades before recently being rediscovered in Yale University’s archives and finally published.