Stephen Hawking, now Lucasian Professor of Mathematics at Cambridge, has been a giant in cosmology for a score of his 40-odd years (an accomplishment perhaps not too startling since the theoretical sciences favor youthful invention). But Hawking is also exceptional in physical stamina. Over the same time span he has lived with amyotrophic lateral sclerosis (lately diagnosed in Jacob Javits), an incurable neuromuscular wasting disease that eventually arrests the muscles of respiration. (Hawking's speech is already seriously affected.) The mind remains intact, however, and journalist Boslough, admittedly admiring to the point of awe, regards Hawking as almost purely a cerebral creature. The slim volume he has written, an outgrowth of a Science article (not the New York Times Magazine piece of last year), succeeds in capturing that turn of mind: the brilliance, impatience, self-assuredness, outspokenness, with only occasional flickers of doubt. (On some colleagues' turning to Eastern mysticism to gain insight into particle physics: ""It's pure rubbish."") Hawking's unabashed goal is ""a complete understanding of the universe, why it is as it is and why it exists at all."" Toward that end Hawking has explored (and is best known for) his ideas about black holes, unshrinkable event horizons, and the existence of myriad mini-black holes capable of exploding and emitting showers of high energy gamma rays. He shares with Paul Davies (below) an interest in the compelling problem of unifying the four fundamental forces of nature; but he is decidedly more skeptical about current theories and findings. The answers Hawking sees--and seeks--lie in the first instants following the ""singularity"" that gave birth to time and space--when indeed there may have been that unity of forces. There is also some discussion of whether the big bang was in reality a bubble or bubbles that might have inflated and then supercooled--with various reasons why such a possibility might resolve certain difficult questions. While Davies' volume supplies more detail on many of these points, a decided plus here is the appendix which presents Hawking's Lucasion Inaugural Lecture entitled, ""Is the end in sight for theoretical Physics?""--nothing less than a summary of 20th-century cosmology with a wry twist at the end. And, for the general reader, the personal focus is an unqualified advantage.