A World Out Of Time

After 200 years in cryosleep, Jaybee Corbell awakens to find that his mind has been downloaded to another body and he's in servitude to a harsh future State. After his escape via a spaceship, he traverses such vast distances--with accompanying time dilations--that he returns to Earth 3 million years later to discover a world wholly alien to the one he'd left. A.E. van Vogt wrote, "This fantastic novel is a mix of Niven hard science and a time-travel concept to boggle the mind."