Parker (physics and astronomy, Idaho State) is that rare teacher who can write and who also is on top of developments in a rapidly changing field. True, the writing reveals the didact--""Let's turn back now to field theory. . .""--but this kind of pedagogy sets up a pleasant tutorial between writer and reader that has distinct rewards. In contrast to the many popularizations on particle physics and grand unified theories (GUTs), Parker begins in the 19th-century--with Dalton and J.J. Thomson (who discovered and named electrons)--and then moves on to Rutherford and Bohr, Planck, de Broglie, Schrodinger, Heisenberg and other superstars who developed quantum mechanics. Just enough personal asides are offered to flesh out the science--we hear, for example, of the classic put-down of a paper by the testy Wolfgang Pauli: ""It's so bad, it's not even wrong."" Particle acclerators, detectors and ""team"" physics play an increasingly important role in the story as Parker deftly sketches the interdependency of theorist and experimenter in positing the existence of, and then discovering, a much-sought-after particle. He is also well aware of the fever pitch of competition that results, narrating the story of almost simultaneous discoveries of a heavy photon particle by Sam Ting at Brookhaven and Burton Richter on the West coast. More important than competition and the clash of personalties, however, is Parker's development of the ideas of contemporary physics, emphasizing the extent to which theorists are guided by considerations of elegance and symmetry. These esthetic considerations clearly governed Gell-Mann's development of the eight-fold way, and the later predictions that new kinds of quarks would be necessary to produce all known particles. Inevitably, as theorists triumphed in unifying electromagnetism and the weak force, more ambitious GUTs or ""T.O.E.s""--theories of everything--would be assayed. Parker concludes with a update on where we stand with the various 10-, 11-, and 26-dimensional theories; Guth's inflationary universe model; superstrings; and other conjectures. It is to his credit that he endows these esoteric conjectures with meaning sufficient to allow an appreciation of their faults as well as their virtues. Well done.