Weinstein, the author of the definitive book on the Hiss-Chambers case (Perjury, 1978), and Vassiliev, a former KGB officer turned journalist, have very effectively raided the KGB archives to gather the fullest account to date of Soviet espionage in the US up to the '50s. Their account reflects not only much of what happened but also the strategies and apprehensions of the spymasters--apprehensions not only about their operations but about their lives, as Stalin's purges eliminated many of the most competent officers. Indeed, one of the surprises is not only the high quality of Soviet personnel up to this time but the extent to which the purges, the defection of Chambers and of courier Elizabeth Bentley, and enhanced counterintelligence virtually crippled much of the Soviet operation in the 1945--47 period. The New Deal period had brought to Washington a number of able sympathizers, moving, like Laurence Duggan and Alger Hiss at the State Department, Harry Dexter White and Nathan Gregory Silvermaster at Treasury, Duncan Lee and Donald Wheeler at OSS, and Lauchlin Currie at the White House, into positions of ever increasing responsibility. The sheer volume of reports flowing out of the Treasury is extraordinary, and the work of Klaus Fuchs, the atomic spy, is in a class of its own. Of Robert Oppenheimer, the authors note that he is named in one report as ""a secret member of the compatriot organization (the American Communist Party)"" but that ""this cannot be independently corroborated"" and that the evidence suggests that he ""never agreed to become a source of information for the Soviets, as some recent writers have suggested."" The authors note that this book cannot be definitive. They didn't have access to all KGB files or any GRU files, nor British or American archives. But it is the most able, careful and comprehensive account we are likely to have for a long time to come.