We are very pleased to announce the publication of Challenge to Apollo: The Soviet Race to the Moon, 1945-1974 (NASA SP-2000-4408), a pathbreaking study by Asif A. Siddiqi. This book is the first comprehensive history, totaling more than 1,000 pages, to appear on the Soviet human space flight program since the opening of the archives in the early 1990s. As a result, it benefits from exceptionally strong primary source materials, as well as perspective on an important challenge that helped to define the U.S. space effort until the 1980s. Going beyond the basic facts, however, Siddiqi has created a gripping narrative that weaves together three broad interpretive themes. The first theme concerns the institutional framework of the Soviet space program and the constituencies that sometimes teamed together and sometimes fought with each other: the engineers, the artillery officers, the defense industrialists, and the Communist Party leaders. These political dynamics lead to the second theme: the Soviet effort to put a human on the Moon before the United States. After the Sputnik triumphs, Soviet military officers quickly lost interest in civilian space activities and felt that such efforts hurt the funding potential for military rocketry. Ironically, the "Cold War, having given birth to the Soviet space program, would seriously threaten its very existence." The third theme of Challenge to Apollo covers the Soviets' methods of technological innovation. Siddiqi challenges the Western conventional wisdom that the Soviets always tended toward incremental, rather than revolutionary, innovation.