Gulag, the searing acronym for the Soviet bureaucracy that administered penal labor camps, ruled a sprawling empire comprising 476 complexes. Each complex contained thousands of individual camps, through which more than 18 million people passed between 1929 and 1953, maybe 3 million or more of whom perished. Applebaum examines this monster from many angles, including its origins, its "function," especially in the Stalinist system, its exponential growth after 1929 and in the 1940s, as well as moments in the "meat grinder" (as it was known): arrest, transit, in, out, and back. Her separate portraits of the guards, the "thieves in law," the common criminals (whose crime may have been coming to work ten minutes late), and the political prisoners (whose transgression may have been telling a political joke) have a special vividness and poignancy. Gulag is a tightly told, complex, heartbreaking, and mind-bending story.