Last and First Men, Olaf Stapledon
This book is very different. It's not so much a story as a history. A history of the entire human race from the first race of man in the present day to the eighteenth race of man some two billion years hence. It takes some getting use to the format and I found the first third of the book, dealing with the first man, to be less interesting. However it is worth going on. I can't help but be impressed by the scale of this book.
