Is 'Moby-Dick' the Greatest American Novel?

Near the beginning of his long narrative poem “Letter to Lord Byron,” W. H. Auden writes, “I want a form that’s large enough to swim in.” So too, apparently, did Herman Melville for his sixth book, when the thirty-year-old author decided to enlarge and deepen a relatively straight-forward nautical adventure story, somewhat in the vein of his first and greatest success, Typee: A Peep at Polynesian Life (1846), and make it…what exactly?