Simak, Clifford D. Time and again. New York: Simon and Schuster, 1951.

Summary: In the eighty-first century, a star-faring explorer returns from a twenty-year voyage, having made first contact with the technologically advanced but standoffish inhabitants of a remote star system. He manages to get back without food, air, water, or working engines, but declines to say how. In order to explain what he learned, he plans to write a book, This is destiny. But time travelers from his future undermine his motivation for a time by revealing that the religion founded on his book will divide into schisms, including at least one that systematically undermines everything he plans to say in the book. After some intricate spatiotemporal adventures, he eludes the time travelers and retires to an out-of-the-way retreat to write the book anyway, hoping that it will cause human beings to treat androids (artificially created people) and robots as equals. He is assisted in his efforts by various supportive androids and robots, who do indeed behave a lot like people, only more polite.

This pretentious, overwrought work is actually free of philosophical content. Although it introduces some ingenious science-fiction gimmicks, it doesn't develop any of them thoughtfully or consistently.