The First Circle by Aleksandr Isaevich Solzhenitsyn
The First Circle is about a distinguished mathematician, Gleb Nerzhin.
December 1949, Moscow, Nerzhin was thirty-one years old and survived the second world war at the German front and the post-war prison and labor camps.
During the story, you get the views from multiple prisoners, each bearing an unforgettable narrative.
I suggest reading the 2009 version instead of the 1968 version, as the 1968 version was censored quite a lot out of fear of the Soviet Union.