This is not an easy book to appraise. The author claims to have been a high official in the Soviet secret service who -- only at the end of 1937 -- decided to break with Stalin for personal reasons. His words are those of a renegade and his mentality that of a master spy. Under these circumstances it is probably surprising that his account is as credible as it appears to be. On the whole, Krivitsky (whose original name was Samuel Ginsburg and on whose rank of "general" doubt has been cast) seems much more reliable in reporting events which he observed at close hand than in discussing those he merely heard about at second hand, such as Soviet intervention in Spain.