"Pick a good model and stay with it," Henry Ford once said. No, he was not talking about cars; he was talking about marriage. Was Clara Bryant Ford a "good model"? Her husband of fifty-nine years seems to have thought so. He called her "The Believer," and indeed Clara's unwavering support of Henry's pursuits and her patient tolerance of the quirks and obsessions that accompanied her husband's genius made it possible for him to change the world...