On the scale from "totally fictional" to "totally non-fictional", Ivan Denisovich leans pretty far to the non-fiction side since much of it is directly based on the author's real experiences, so much so that it's often referred to as a "semi-autobiography".

As one of "them" who often prefers non-fiction, I enjoyed the book for that reason. Incidentally, I think it's stronger in this fictionalized form than as it would have been as a straight-up autobiography.