"Engrossing. . . . Gellman is] a thorough, exacting reporter . . . a marvelous narrator for this particular story, as he nimbly guides us through complex technical arcana and some stubborn ethical questions. . . . Dark Mirror would be simply pleasurable to read if the story it told didn't also happen to be frighteningly real." --Jennifer Szalai, The New York Times From the three-time Pulitzer Prize winner and author of the...