This collaboration by two masters of the genre expands on Asimov's classic short story first published in 1941. Kalgash is a planet with six suns, a world where darkness is unnatural. Scientists realize that an eclipse--an event that occurs only every 2049 years--is imminent, and that a society completely unfamiliar with darkness will be plunged into madness and chaos. The novel traces events leading to this discovery, and the fates of the main characters immediately following the apocalypse. While the premise is convincing in the context of a short story, this longer version brings up too many unresolved questions. The original tale was tightly written, succinct and stunning, but the novelization seems flabby and drawn-out--the reader recognizes the significance and consequences of the impending events long before the characters do. An abrupt and simplistic ending further mars a hallowed SF tale. 100,000 first printing.