The Time Machine by H. G. Wells

The Time Traveller, a dreamer obsessed with traveling through time, builds himself a time machine and, much to his surprise, travels over 800,000 years into the future. He lands in the year 802701: the world has been transformed by a society living in apparent harmony and bliss, but as the Traveler stays in the future he discovers a hidden barbaric and depraved subterranean class. Wells's transparent commentary on the capitalist society was an instant bestseller and launched the time-travel genre.