Radzinsky (Russian: Эдвард Радзинский) is an author of more than forty popular non-fiction books on historical subjects. Since the 1990s, he has written the series Mysteries of History. The books translated to English include his biographies of Tsars Nicholas II and Alexander II, Rasputin, and Joseph Stalin. His book Stalin: The First In-depth Biography Based on Explosive New Documents from Russia's Secret Archives discusses a number of well known controversies about Joseph Stalin, including the existence of a fuller text of Lenin's Testament, the alleged involvement of Stalin as an agent of the Tsarist secret police, and the role of Stalin in the death of his wife and the murder of Sergey Kirov. According to Radzinsky, Stalin was poisoned by order of Lavrentiy Beria. His book includes an interview with a former bodyguard of Stalin, who stated that on the night of Stalin's death, the bodyguards were relieved of duty by an NKVD officer named Khrustalev. This same officer was briefly mentioned in Memories, the memoir of Stalin's daughter Svetlana Alliluyeva. Radzinsky also supported the hypotesis by Viktor Suvorov that Stalin had prepared a preemptive strike against Nazi Germany