This is the book that put Furst in the top tier of spy novel writers. The story gives a chilling picture of how the NKVD operated in the 1930s and during WWII. It opens with the recruitment of Khristo Stoianev of Bulgaria in 1934. An agent of the Soviet spy network convinced him that the NKVD was the place for him.
He joined a class of men pulled from many of the Balkin countries to be formed into hardened operatives for the Mother Land. If you wonder how it was that the Soviets were able to take control of Eastern Europe so easily after the war, here is your answer. Warning: if you know little about the old Soviet Union, especially under Stalin, this can be rough sledding.
The story generally follows Khristo, but ventures off onto other members of his class from time to time. A couple of Americans show up during the war, working with the OSS and sometimes working with Khristo.
I have been a sometime student of the USSR, first as a history undergraduate and later as a graduate student in political science. I have read widely, though not deeply, enough to have a decent understanding of Russian thinking. They are pessimistic and distrustful. They took the work of Karl Marx and turned it from science (however flawed) into a religious potion akin to voodoo.
Whatever else happened in the Thirties, Stalin wanted a large barrier between Russia and Europe. To do that he gave the NKVD the job of quietly undermining the target governments by converting strong men into their spokesmen and their killers. They infiltrated every country in Europe to greater or lesser success. They even targeted the US, though with little effort until after WWII.
This is one of those sweeping novels that can spend ten pages on one boat trip. Not to fear, things happen on that trip.
There are good reasons to read this book, including the fact that it is the first in a series of fifteen books that Furst calls “chapters” in one long story.