Asimov wears two hats, one as genial science popularizer and another as popular science-fiction writer, in this odd fact-and-fiction combination of 12 essays (1969-82, from The Magazine of Fantasy and Science Fiction) and a dozen stories (1941-85, including one original). The idea is to encourage fiction readers to tackle the non-fiction, and vice versa. Under the general theme of "scientists," the essays ramble--in the usual amiable, modestly informative, sometimes trivializing Asimov style--through such topics as: Newton's classic experiment in splitting white light into the colors of the spectrum; Herschel's solid scientific legwork in discovering the planet Uranus; the hoary yam about Archimedes and his bath ("Eureka!"), and that geometer's delight, Euclid's (unprovable) Fifth Postulate. Alternating with the essays, the stories include some of Asimov's best, most famous, oft-anthologized works. "Nightfall" concerns a planet with several suns, where darkness falls only once in thousands of years. A Neanderthal child is brought into the present as a cynical publicity stunt in "The Ugly Little Boy." There's "Pate de Foie Gras," about a radioactive goose that lays real golden eggs. Super-computer Multivac becomes God in "The Last Question." And the invention of a time-scanner brings an end to personal privacy in "The Dead Past." So, with one feeble exception, this is familiar stuff, readily available elsewhere--though a few unwary readers may be fooled by the packaging gimmick.