This account of the Cambridge Spy Ring is so knowledgeable and full of insight that it sweeps the competition from the field. Modin has a unique perspective. As a young man in the KGB, from 1944 until 1947, he translated, assessed, and passed on the extraordinary output of the Cambridge Five: Guy Burgess, Donald Maclean, Kim Philby, Anthony Blunt, and John Cairncross. From 1948 to 1951, he was their KGB controller in London. During this time he got to know Burgess, Blunt, and Cairncross well, although he didn't meet either Philby or Maclean until later, in Moscow. What makes this memoir so superior is not just Modin's firsthand knowledge but the modesty and perceptiveness of his analysis. He describes Burgess--often portrayed by others as a drunken, lecherous homosexual--as the real leader of the group, who held it together and was in fact its moral center. Blunt, who later became one of the most famous art historians of his time, had ``an uncanny ability to win the confidence'' of colleagues in British counterintelligence, who spoke to him with appalling candor about their operations. Cairncross was the first agent to notify the Soviet government of the work being done to develop the atomic bomb. But Modin's highest accolades go to Philby, whom he thinks the greatest spy of the century for the thoroughness and accuracy of his information, and to Maclean, whose political intelligence may ultimately have been even more valuable. Modin presents the five as true believers in world revolution who were nevertheless aware, and highly critical, of Soviet imperialism. They remained, Modin says, passionately in love with England. As for himself, Modin is proud of the competence with which he and his spies performed. But time has clearly eroded his respect for ideology: In closing, he describes the Cambridge Five as men who ``chose to follow the greatest illusion of all, which is politics.'' Almost certainly the best book on this subject that we are likely to see.