"Gravity's Engines" is a book of two parts. The first provides a thorough and workmanlike account of black holes—the "engines" of the title—for the nonscientist. Although several other books have set out to cover much the same ground, there is always room for another, and this one has the advantage of being, for the moment, the most up-to-date.
Of course, there is no point in being up-to-date unless the story is told accurately, and Caleb Scharf, who is the director of Columbia University's Astrobiology Center, clearly knows his stuff. The ingredient that he adds to the mix is his interest in the origin of life and the role that black holes have played in creating the conditions suitable for life. This is the theme of the second part of the book, which becomes the narrative of a personal drama as Mr. Scharf describes his own research and the combination of serendipity and hard work that has led him to arrive at various insights and discoveries. The second part of "Gravity's Engines" lifts the book well above its competitors.