Brief it is. Also dizzying, exhilarating, and not a little daunting. Hawking is a legend in his time: at 44, he holds the Lucasian Chair in Mathematics in Cambridge--heir to Newton and widely regarded as one of the most brilliant and influential theoretical physicists in the world. Legend also surrounds Hawking for his valiant struggle against amyotrophic lateral sclerosis, an incurable neurological disease that progressively weakens the neuromuscular system, but clearly spares the brain. Hawking tackles cosmology theories here, summarizing the early 20th-century contributions of Planck in the development of the concept of the quantum, and Einstein's special and general relativity theories. Man's quest for unified theories, for answers to fundamental questions on the nature and destiny of the universe, have given rise to legend, to religious dogma, and, most recently, to many visions and revisions of grand unified theories, ""supergravity,"" string theories, and multi-dimensional and inflationary universes. Hawking traces his own visions and revisions, beginning with his well-known concepts of black holes (big, mini, primordial) and other singularities that may define the origin and collapse of the universe, He also explains how he has altered his thinking to allow emissions from black holes. (They occur in the virtual empty space surrounding the hole.) Ultimately, he postulates the concept of a universe that is finite but unbounded--something like the surface of a sphere but occupying ""imaginary"" time. Flirting with the weak anthropic principle--the idea that the universe is the way it is because if it were different we would not be here to observe it--Hawking concludes with the hopeful thought that within the generation some marriage of quantum mechanics and gravity may unity physics and, with it, explain the common unidirectionality of the cosmological, thermodynamic, and psychological arrow to time. In spite of a lucid, even deceptively simple style, these are heady concepts. An elegant feast for cosmological gourmets, perhaps, but others may have problems digesting.