Agreed, one of my favorite pieces of literature. It's what got me into American historical fiction - I later ventured into Steinbeck and Mark Twain, both of whom are masters of the genre.
Love Twain and Steinbeck (most especially other works than Grapes of Wrath). Great Gatsby didn't work for me when I read it recently - just not my thing. I loved Catch 22 because I hadn't realized it was a comedy before I read it. It's tough because too often the best known past authors are unenjoyable to read.