At its height, says Volodarsky, the Soviet Union had the largest biological warfare program in the world. Sources have claimed there were 40,000 individuals, including 9,000 scientists, working at 47 different facilities. More than 1,000 of these experts specialized in the development and application of deadly compounds. They used lethal gasses, skin contact poisons that were smeared on door handles and nerve toxins said to be untraceable. The idea, at all times, was to make death seem natural — or, at the very least, to confuse doctors and investigators. “It’s never designed to demonstrate anything, only to kill the victim, quietly and unobtrusively,” Volodarsky writes in The KGB’s Poison Factory. “This was an unbreakable principle.”
The Soviet biowar program was largely due to the Soviets' sense that they couldn't catch up with the US nuclear program, so they doubled down on biological warfare. This fact was not known at the time of the fall of the Berlin Wall and has only come out slowly over time (and very much not publicized). Biopreparat was no joke, and any "secret" toxins they may have come across were a side effect of the development of doomsday-level toxins.
Other than that, a gripping and engaging read.