This timely book is suitable for the general reader wishing to find answers to some of the intriguing questions now being asked about black holes. Although once recognized as the most destructive force in nature, following a cascade of astonishing discoveries, the opinion of supermassive black holes has undergone a dramatic shift. Astronomers are discovering that these objects may have been critical to the formation of structure in the early universe, spawning bursts of star formation, planets, and even life itself. Fulvio Melia is Associate Head of Physics and Professor of Astronomy at the University of Arizona. He is author of Electrodynamics (University of Chicago, 2001), and a forthcoming title, The Black Hole at the Center of Our Galaxy (Princeton).