He is almost totally paralyzed, speechless and wheelchair-bound, able to move only his facial muscles and two fingers on his left hand. He cannot dress or feed himself, and he needs round-the-clock nursing care. He can communicate only through a voice synthesizer, which he operates by laboriously tapping out words on the computer attached to his motorized chair. Yet at age 50, despite these crushing adversities, Stephen Hawking has become, in the words of science writers Michael White and John Gribbin, "perhaps the greatest physicist of our time." His 1988 book, A Brief History of Time, has sold 1.7 million copies around the world.

Hawking's choice of career was most fortunate, for himself as well as for science. Rejecting the urging of his physician father to study medicine, Hawking chose instead to concentrate on math and theoretical physics, first at Oxford and then at Cambridge. But at age 21 he developed the first symptoms of amyotrophic lateral sclerosis (ALS), a disorder that would inevitably render him paralyzed and incapable of performing most kinds of work. As the authors note, theoretical physics was "one of the very jobs for which his mind was the only real tool he needed."

He has used that tool with consummate skill. While still a graduate student, Hawking became fascinated by black holes, the bizarre objects created during the death throes of large stars. Working with mathematician Roger Penrose and using Einstein's relativity equations, he developed new techniques to prove mathematically that at the heart of black holes were singularities — infinitely dense, dimensionless points with irresistible gravity. He went on to demonstrate that the entire universe could have sprung from a singularity and, in his 1966 Ph.D. thesis, wryly noted that "there is a singularity in our past."

Gathering momentum as a fellow at Cambridge, Hawking calculated that the Big Bang, which gave birth to the universe, must have created tiny black holes, each about the size of a proton but with the mass of a mountain. Then, upsetting the universal belief that nothing, not even light, can escape from a black hole, he used the quantum theory to demonstrate that these miniholes (and larger ones, too) emit radiation. Other scientists eventually conceded that he was correct, and the black-hole emissions are now known as Hawking radiation.

Engrossed as Hawking is with his work, the authors say, "ALS is simply not that important to him." He certainly does not dwell on his handicap. His succinct, synthesized-voice comments are often laced with humor, he enjoys socializing with his students and colleagues, attends rock concerts and sometimes takes to the dance floor at discos, wheeling his chair in circles. But he can be stubborn, abrasive and quick to anger, terminating a conversation by spinning around and rolling off, sometimes running one of his wheels over the toes of an offender.

Hawking can also be wrong. In 1985, for example, he brashly proclaimed that when and if the universe stopped expanding and began to contract, time would reverse and everything that had ever happened would be rerun in reverse. Eighteen months later, he sheepishly admitted his mistake. Earlier, after trashing another scientist's notion that the 19th century theory of thermodynamics could be applied to black-hole theory, he recanted and began applying it himself.

Without his wife Jane, Hawking has always emphasized, his career might never have soared. She married him shortly after he was diagnosed with ALS, fully aware of the dreadful, progressive nature of the disease, giving him hope and the will to carry on with his studies. They had three children in the early stages of their marriage, and later, as he became increasingly incapacitated, she devoted herself to catering to his every need.

After years of apparently harmonious marriage, however, rights began appearing. As the accolades and awards poured in for Stephen, Jane — competent and intelligent in herself — began to resent living in his shadow. Deeply religious, she was also offended by his apparent atheism. Particularly galling to her was his concept, enunciated first before the Pope at a scientific meeting at the Vatican, that the universe might be completely self-contained, having no boundary or edge, no beginning or end. "If that were true," he asked provocatively, "What place, then, for a creator?" Still, friends were shocked in 1990 when Hawking abruptly ended their 25-year marriage, moving in with one of his nurses.

What this book brings to the already crowded domain of Hawking lore is a rather successful merger of biography and physics. As it traces the course of Hawking's life, it pauses occasionally to prepare the reader for the mind-boggling complexities of relativity theory and the even more bizarre notions of quantum physics — twin pillars on which Hawking has constructed his theories — which he is currently attempting to unite in an all-encompassing theory. The authors characterize their early review of Newton's classical theory of gravitation, for example, as "a gentle workout in the foothills before we head for the dizzy heights."

The exercise works. By the time the higher elevations are reached, such strange notions as Einsteinian curved space-time and the quantum uncertainty principle, heavy meals indeed, seem not so difficult to digest.

Still, it is the man, more than the science, who dominates this book, with his triumph over a terrible affliction, his courage, his humor and his admirable lack of self-pity. As Hawking's computer voice declared during the final scene in a BBC TV show, "I have a beautiful family, I am successful in my work, and I have written a best seller. One really can't ask for more."