Nightfall lacks the fast pacing typical of the adventure novels of Asimov and Silverberg; it is not an adventure novel in spite of its adventure structure, featuring the struggle of a few sane people to reach safety. It is instead an "idea" or "concept" novel. Science fiction often focuses on an idea that it ex3688 Nightfall plores. Characterization and plot are often subordinated to the theme—or main idea—of the story. Nightfall is plainly a study of the effects of a revolutionizing new view of the universe upon people who are utterly unprepared for it.

In this, Nightfall examines a phenomenon that has occasionally occurred in earthly cultures. For instance, the landing of men on the moon had a stunning effect on people; there were numerous reports at the time of suicides by people who simply could not live with the idea that...