Alone onstage, the god Apollo summons music to pour forth from his lyre. He is joined by the muses Calliope, Polyhymnia, and Terpsichore. Tentatively they approach, drawn by his song. He looks at them, and they bow respectfully. He kneels on one leg and elevates the neck of his instrument while the muses surround him, lifting their legs behind them in an arabesque penché. At the apex, held for just a moment, there are four long parallel lines. It takes one’s breath away. The choreographer of Apollo, this masterwork of twentieth-century ballet, was George Balanchine (1904–83). He was twenty-four years old.

Jennifer Homans is an ideal guide to Balanchine’s life and accomplishments. The current dance critic at The New Yorker, she is also a Distinguished Scholar in Residence at New York University. Ten years went into the making of Mr. B, which is meticulously researched and informed by interviews with nearly two hundred former Balanchine dancers. To her work Homans brings the perspective of a practitioner. As a teenager, she trained at the School of American Ballet and had the chance to watch Balanchine in action. She danced professionally into her mid-twenties.

The first part of Mr. Bconcentrates on Balanchine’s early years in Russia, the part of his life that is perhaps less widely known. Balanchine—Georgi Melitonovich Balanchivadze—was born in 1904 in St. Petersburg. His Georgian father, Meliton, a composer and choir director, was often absent and a spendthrift with his