In 1949, the British ballerina Margot Fonteyn gave her first performance in America. She enchanted her New York audience, including a young man named Robert Gottlieb. Gottlieb grew up to be a prestigious book and magazine editor (he recently edited Bill Clinton’s memoir) but he has continued to be captivated by ballet, and by the magic of Margot Fonteyn. Thirty years after editing Fonteyn’s biography, he has organized an exhibit at the New York Public Library called Margot Fonteyn in America: A Celebration. Kurt Andersen visits the exhibition with Bob Gottlieb.