What is the theme in Khrushchev by William Taubman?

Pre-emption is a major theme in this book. Do unto others before they can do it to you is a major precept of the Soviet leadership, beginning with Stalin's elimination of the original Bolshevik Old Guard, then the generals who might use their troops to oppose the Soviets, and then devolving into wholesale, indiscriminate bloodshed. Stalin's lieutenants, encouraged not to trust one another or socialize, live in constant fear of provoking his wrath, but even Beria, who controls the secret police, knows Stalin is untouchable (although Beria claims enigmatically to have saved his colleagues the trouble of killing Stalin by somehow arranging his demise in 1956).