Weinberg's career has gone from boy wonder to Nobel laureate (Physics, 1979) to sage among particle physicists, combining creative talents with a zeal to explain. In The First Three Minutes (1977), he popularized Big Bang cosmology, in particular the symmetry-breaking changes and events that can account for the matter-filled universe around us. Now, 15 years later, he summarizes how far theory has gone toward uniting gravity, electromagnetism, and the weak and strong nuclear forces into a final theory. To accomplish this summary requires a masterful backing-and- filling of 20th-century physics, spelling out the role of Einstein in 1905 and 1917, Einstein's dispute with Bohr, the Copenhagen interpretation, the contributions of Heisenberg, Dirac, Schrîdinger, and Feynman, and so on down to the younger generation of string and superstring theorists. This would be enough for a popularization, but Weinberg has something else in mind. He discusses, from an insider's point of view, the style of science, specifying concepts like beauty and simplicity, and the context of science, describing the social milieu that creates waves of belief (or disbelief) at given times. Mirabile dictu, he also devotes a chapter to religion, seeing its role as a consolation in the face of death--something science cannot offer. But the underlying theme and not-at-all-hidden agenda emphasizes that if we are going to make any headway toward a final theory, it can come about only with the discovery of entities such as the Higgs particle, using equipment like the Super Collider. While Weinberg justifiably extols the explanatory power of 20th-century quantum mechanics, then, he leaves the reader with the frustrating sense that politics, the recession, science-infighting, or any combination thereof may thwart the logical next step. He makes an eloquent case.