Groundbreaking, transcendent, 1931 science fiction novel/future history, by Olaf Stapledon. Last and First Men's supremely ambitious goal is nothing less than to describe the entire history of the evolution of humanity, through some eighteen different species and two billion years. The book bucked the science fiction traditions of its time by focusing very little on technology and grand space opera-style conflicts, taking as its subject instead the moral, social and spiritual changes that Stapledon envisioned over the vast scope of time he covered.
Much of the scientific and technological speculation that Stapledon does include is laughable, and even his view of evolutionary processes seems skewed and almost Lamarckian. The more recent future history (from 1930 to the present) is also, obviously, wrong, though not as wrong as one might expect: from the comfortable period after the "War to End All Wars" he predicts more world wars, and eventually a near-holocaust through the use of plausible, though not quite right, weapons of mass destruction.
To complain about these deficiencies is mostly to miss the point, though. The whole idea of a book written with two billion years of future history as its subject was a totally new idea at the time, and even now, a modern reader can marvel at the sheer staggering ambition of the project, and the way that Stapledon brings everything together in broad believable strokes, with themes cropping up, intertwining, dissapearing, and then reappearing again, millions of years later, to combine in some new way: history as symphony.
At the time of its publication, Last and First Men created a fairly immediate stir, and quickly became enormously influential. Many movements and tropes in science fiction can be traced back to it: the idea of future history as worthwhile project, and the prospect of speculative fiction as a vehicle for social and cultural commentary, rather than pure technological gee-whizzery. Frank Herbert's Dune and Asimov's Foundation series in particular can be seen as direct and linear descendants of Last and First Men
The book was, inexplicably, out of print in the States for many years, though it has recently been republished, in an omnibus edition with Stapledon's even more ambitious, though less successful, Star Maker.