H. G. Wells 
The Time Machine 

The Time Machine was the first of a number of these imaginative literary inventions. First published in 1895, the novel follows the adventures of a hypothetical Time Traveller who journeys into the future to find that humanity has evolved into two races: the peaceful Eloi — vegetarians who tire easily — and the carnivorous, predatory Morlocks.
After narrowly escaping from the Morlocks, the Time Traveller undertakes another journey even further into the future where he finds the earth growing bitterly cold as the heat and energy of the sun wane. Horrified, he returns to the present, but soon departs again on his final journey.
While the novel is underpinned with both Darwinian and Marxist theory and offers fascinating food for thought about the world of the future, it also succeeds as an exciting blend of adventure and pseudo-scientific romance.