My experience with "The Classics" is pretty limited. I know this category can entail all genres and may have been written a few decades ago or a few millennia ago. I would like to read something that isn't going to take me two painful months to finish but still want something of a challenge. Therefore, I am asking you, fellow RAFO visitors, to help me decide. What is the best "classic", in your opinion. I had a few I was considering (Slaughterhouse Five, The Man In High Castle, Middlemarch) but wanted to hear some good suggestions. I will probably get started on this early next week, so I hope I get some good feedback!

EDIT: I would appreciate only classics that are in English. I know translations rarely do full justice to the original language novels but I'd have some great difficulty finishing the book otherwise.