Comets, supernovae, black holes, and quasars are among the "monsters" of the book"s title—extraordinary astronomical bodies and phenomena that scientists now believe are the key to understanding the rules of the universe. Monsters in the Sky is the sequel to Paolo Maffei"s popular Beyond the Moon (MIT Press, 1978), which gave lay readers a grand tour of the natural order of the universe. Beginning with comets, Monsters in the Sky moves outward from our solar system, from one enigma to the next, ending with those farthest removed, the invisible "hidden mass" of galactic clusters extremely distant from us. Between the comets and the hidden galactic mass, the book"s topics include: satellite clouds, dust rings, cyrillids and tektites, the mysterious planet Vulcan, nebulae and novae, super-supernovae, "runaway stars," the future of our own star, X-rays, the probable cause of the dinosaurs" demise, black holes (probably one of the best discussions of this subject), white holes, journeys through space-time, BL Lacertae objects, Markarian, N, and Seyfert galaxies, quasars, and anomalous red shifts.