For some readers and critics Robert Lowell stood at the center of his literary generation, and by the mid 1960s one admirer, Irvin Ehrenpreis, was referring to "The Age of Lowell." One can see why. Lowell was associated with nearly all the important American poets of the first half of this century, and long before the end of his life he seemed to be their heir. His appeal was not only literary. He involved himself to an unusual degree with the public events of his time, just as he brought his private life into public view by way of his poems. He was at once the poet of the American empire (sometimes resembling Virgil, sometimes Juvenal, sometimes Horace) and the alleged father of "confessional poetry." He wrote a great deal during his last decade, from 1967 to 1977, but so far few readers have assimilated the late work. His great...