As befits a National Geographic writer, Boslough literally traveled around the world in the last decade to gather material for this analysis of cosmology today. The result was an end to the author's own innocence: He admits to an earlier romanticism and awe in the presence of eminent cosmologists, as evidenced in his 1984 Stephen Hawking's Universe. Not anymore. The truth, as Boslough reports it, is that observational astronomy is way ahead of the theorists. With more and better instruments to scan the far reaches of the universe, facts are accumulating that defy theorists' armchair/computer visions: The Great Wall (or walls) of galaxies that give the lie to homogeneity in the universe; the Great Attractor that holds our local cluster of galaxies in gravitational sway; quasars of fantastic brilliance out there at 14 billion light-years (too soon after the birth of the universe by current conventions)...and when you combine that with the fact that nobody has come up with a plausible explanation for the so-called ``dark matter'' (estimated to represent 90 percent of the mass of the universe) or proven the existence of black holes, or been able to unite gravity with electromagnetism and the weak and strong nuclear forces in any Grand Unification Theory, the time for a new paradigm must be at hand. Boslough doesn't leave the reader in suspense, saying at the outset that cosmology is in deep trouble. And to prove his point, he gracefully backs and fills, providing sketches of the key players and ideas that have colored 20th-century visions of astro- and-quantum physicists (and revisions, too, as he notes the many fixes and even about-faces in the various models proposed). All this is told in an informative, congenial, and nonvindictive style: After all, you never know where the next paradigm will come from.