The murky relationship between reality and our knowledge of it is one of philosophy's most famous conundrums. According to this engaging tour of contemporary information science, the question may be moot since, if some theorists are to be believed,""the stuff of the world is really, at bottom, information."" That may be the sort of grandiose claim cyber-enthusiasts make when they get a new Palm Pilot, but physics professor and journalist von Baeyer (Warmth Disperses and Time Passes) manages to invest it with real intellectual substance. Delving into the history of science from ancient Greek theories of the atom to the frontiers of astrophysics, he shows how the concept of information illuminates a huge variety of phenomena, from black holes to the gamesmanship strategies of Let's Make a Deal. Along the way, he provides a lucid and easily accessible treatment of some fairly sophisticated topics in thermodynamics, communications theory and quantum mechanics; his account of such aspects of""quantum weirdness"" as superposition and action-at-a-distance, in which the law of the excluded middle is repealed (e.g., how Schrodinger's cat is both alive and not alive) and particles seem to have an eerily telepathic knowledge of regions of space where they have never been, is a tour de force of popular scientific exposition. Von Baeyer manages to steer clear of equations without resorting to the hand-waving metaphors that too many science popularizers lapse into when trying to convey difficult ideas. The result is a stylish introduction to one of the most fascinating themes of modern science.