The Underground Railroad by Colson Whitehead
My rating: 4 of 5 stars
Hard to read without grimacing at some points, but nevertheless enlightening. It assumes the Underground Railroad was a literal railroad (some reviewers call it an alternate history, even listing it as science fiction), but it is told in a very matter-of-fact way, and it is believable. Cora's run for freedom is thwarted and minimally rewarded by turns, and hopeful, too. But man oh man, some scenes are so realistic and depressing.
Highly recommended for a one-time read as it was a Pulitzer Prize winner, but I doubt you would want to read it again for enjoyment.