I’ve read many, many books on the period in question, but the best is probably “The Soviet Tragedy: A History of Socialism in Russia, 1917-1991” by Martin Malia. Tragedy is the right word, except that it cannot even remotely capture the disaster of the Soviet era, at every level and from every perspective. I can hardly even think of that time without recounting all the stories of the individual lives destroyed; it was an evil of unfathomable proportion, and the only response I can think of that is appropriate for a civilized man is to weep in recollection. All those pour souls; Putin and his criminals are shoveling dirt on their memories once again.