You can read One Day In the Life of Ivan Denisovich in a night, I stayed up all night reading it years ago. The Gulag is very long and more difficult, hard to put down but also so intense it’s better to put down in between readings.
Amazing book, our entire class read it in High School.
One learns to value the little things in life...
Go to youtube search for “The Chekist 1992 English subtitles” unless your Russian is good! Watch it! Grim movie in the Russian literary psychological drama tradition. Remember this movie was released one year after the fall of the Soviet Union.