The Gulag Archipelago
The Gulag Archipelago is Solzhenitsyn's masterwork, a vast canvas of camps, prisons, transit centres and secret police, of informers and spies and interrogators and also of heroism, a Stalinist anti-world at the heart of the Soviet Union where the key to survival lay not in hope but in despair. The work is based on the testimony of some two hundred survivors, and on the recollection of Solzhenitsyn's own eleven years in labour camps and exile. It is both a thoroughly researched document and a feat of literary and imaginative power.
Note: this is a used book.