The Time Machine by H. G. Wells
Apparently I had no idea what The Time Machine was about, aside from the obvious of course. The Time Traveler has invented a machine that can go into the past or travel into the future, but of course his friends, who he has dinner with weekly, don't believe him. However, the next week, he shows up late to his own dinner party looking ragged and disheveled and tells his friends an incredible story of traveling into the distant future. There he discovers two bizarre races—the ethereal Eloi and the subterranean Morlocks—who not only symbolize the duality of human nature, but offer a terrifying portrait of the men of tomorrow as well. He also tells of going even farther and seeing the dying planet.
On the one hand, it's an interesting exploration of class and societal evolution. It's the first story to popularize time travel and the image of the dying earth, not the one of the Eloi and Morlocks, but of the...