On August 6, 1945, the world was electrified by the news that an American Army bomber had dropped an atomic bomb, with an explosive power equivalent to 20,000 tons of TNT, on the important Japanese military center of Hiroshima. Three days later another bomb, of improved design and even greater power, was dropped on Nagasaki. The following day, Aug. 10, the Japanese sued for peace. Newspapers and magazines throughout the world printed many thousands of words about the new weapon and the scientific developments that had made it possible. These stories were based largely on official War Department releases prepared by William L. Laurence, science reporter for The New York Times. At the request of the War Department, Mr. Laurence had been granted a leave by The Times several months earlier. Mr. William L. Laurence was the only newspaper man permitted by the War Department to go to all the plants and inspect the processes of production of the atomic bomb, the only newspaper man allowed to witness the secret trial of the bomb in New Mexico, and the only newspaper man who witnessed the actual dropping of one of the bombs on Japan, from a plane above Nagasaki. This book, first published in 1946, is the full story, so far as it may yet be revealed, of the atom bomb, written by the man who is unquestionably the best qualified to write it for the layman.