Time

I have at last managed to read Stephen Hawking's "A Brief History of Time" from "We go about our daily lives understanding almost nothing of the world" through to "Zeldovich, Jakov, 114, 115". I can't claim to have understood all of it, but actually finishing seems quite an achievement. One of the great unfinished books, like Will Hutton's "The State We're In" and Mishima's "The Sea of Fertility". What other great unfinished books are there?