At midlife, Mary Rose O'Reilley writes, we are called to an "archaeology of memory"--turning over a potsherd here, a fragment there--to assemble something whole out of the messiness of experience. Excavating her own life, she traces the middle-class Irish American background that shaped her, with its mix of antic humor, terror, and mysticism, and finds meaning in the seemingly smallest, most transient encounters. But O'Reilley's...