I can recommend (if that is the correct term) the book "Stalin: The Court of the Red Tsar" for a chilling description of the leadership of the Soviet Union from the early 30s until Stalin's death:

http://www.amazon.co.uk/Stalin-The-Court-Red-Tsar/dp/0753817...

http://www.amazon.com/Gulag-History-Anne-Applebaum/dp/140003...

http://en.wikipedia.org/wiki/The_Gulag_Archipelago

http://www.amazon.co.uk/Stalin-Court-Simon-Sebag-Montefiore/...

http://www.amazon.co.uk/Whisperers-Private-Life-Stalins-Russ...