Against the Fall of Night by Arthur C. Clarke

When readers think of Arthur C. Clarke's works, perhaps 2001: A Space Odyssey or Rendezvous with Rama are the most often remembered. But my favorite novel by Master Clarke will always be Against the Fall of Night.

Imagine an Earth of salt and sand, where oceans are a memory millions of years old and the remnants of humanity have gained great longevity even as their population dwindles away in an immortal city of machines. Alvin is the last child born in the Port of Diaspar in seven thousand years, and far too curious for his own good. He embarks on a forbidden quest to seek answers beyond the city's crumbling walls: is there anyone, any life at all beyond Diaspar? Who were the Invaders that pushed man's empire from the stars and nearly destroyed the human race?

Alvin's lonely restlessness holds the reader captive till the last page, and makes his journey, your journey.