At Twelve is a composite portrait that is both universal and intimately personal. As Ann Beattie writes in her perceptive introduction, "These girls still exist in an innocent world in which a pose is only a pose--what adults make of that pose may be the issue." Sally Mann's work is in the collections of major museums across the country. "Haunting black-and-white studies of children, shown here as surprisingly sensual and often distant beings, the...