A lucid tour of “the best known and least understood objects in the universe.” A black hole is a region in space where gravity is so strong that nothing can escape, not even light. It’s a concept that has long fascinated astronomers and continues to generate a steady stream of popular science books. In his latest, Impey (Astronomy/Univ. of Arizona; Beyond: Our Future in Space, 2015, etc.) delivers an accessible yet definitely not dumbed-down explanation of this spectacular phenomenon. From its inception, most scientists accepted Einstein’s 1915 Theory of Relativity, which described gravity as a distortion of space-time by a nearby mass. When his equations revealed that immense gravity would distort space-time so much that light would double back on itself, most scientists, Einstein included, assumed this was a mathematical curiosity. It wasn’t. Within the past 100 years, writes Impey, “black holes have evolved from a monstrous idea, one that violates common sense, to a proving ground for the most cherished theories in physics.” An ordinary black hole forms when a star ages, runs out of fuel, and collapses. Most shrink into dwarves, but when this happens to the rare star with a mass greater than 20 times that of the sun, no known force can prevent it from collapsing to an infinitely dense point called a singularity, surrounded by a black hole. Stranger still, at the center of every galaxy, including ours, is an immense “supermassive” black hole containing millions or billions of solar masses. A good writer as well as a specialist in black holes, Impey works hard and mostly successfully to illuminate complex phenomena without resorting to the TV documentary magic show (entertainment trumping explanation) and includes plenty of personal anecdotes, imaginative analogies, and useful illustrations. Readers who remember freshman college physics or astronomy will have an easier time, but few will regret encountering such irresistible astrophysical wonders.