The Smithsonian has a list up of the
Top 10 Books Lost to Time. It's an interesting read, though I expected something more exciting. (Yes, I go to places like the Smithsonian when seeking excitement. Perhaps it's why
I blog so often on boredom.)
Numbers 5-10 are lost and uncompleted novels from Austen, Melville, Hardy, Stevenson, Hemingway and Plath. Most seem more likely to be minor works than monuments (even though I like most of the mentioned authors, or at least their peaks).
Prediction I: We'll unearth at least five novels in the next 40 years that will be more significant than any of these (except perhaps the Austen) would be. They'll probably be something in translation. (This list seems to have a bit of a bias toward English-language works).
Prediction II: There's probably already
a remake of the Austen in the works.