Worlds Enough and Time

In the gripping finale of the Worlds trilogy by Joe Haldeman, humanity faces extinction on a perilous journey aboard the interstellar vessel Newhome, as the Earth has become an uninhabitable shell. Ten thousand colonists, led by Marianne O'Hara, embark on a quest to a potentially habitable planet in a distant star system, but their voyage is marred by sabotage, ignorance, and a nihilistic religion bent on destruction. As they navigate numerous trials and tragedies, the fate of the human race rests heavily on their shoulders, leaving them with no choice but to move forward into the unknown.