THE UNDERDOGS tells the story of Karen Shirk: felled at age 24 by a neuromuscular disease and facing life as an immobile, deeply isolated and depressed, ventilator-dependent patient, she was rejected by every service dog agency in the country as "too disabled." Her nurse encouraged her to raise her own service dog, and Ben, a German shepherd, dragged her back into life. "How many people are stranded like I was," she wondered, "who could lead productive...