Last and First Men and Star Maker by William Olaf Stapledon (1968, Paperback)

These are "the Great Gray Books of Science Fiction" as Theodore Sturgeon once put it. If one reads them, you will believe in God, is what I say. It is like expliring the universe in the macroism. As you read it expands more and more. The theme of the first book is the rise and fall of mankind over thirteen million years, the second book mentions the first as an honorable mention. Like Ulysseus by James Joyce the books are definitely worth the effort that you put into them.