Gustav and Alma Mahler in New York City in 1907: He had been invited to lead the Metropolitan opera; his glamorous wife accompanied him to the New World. Nineteen years his junior, Alma was Gustav's constant companion, occasional soulmate, sometimes his muse, always his caretaker: a woman otherwise restless and unfulfilled. Her husband's life was intensely interior, sporadically alert to others' needs and desires. His energy and idealism were aroused...