"With the exactitude of a surgeon and the sensuous attention of a chef, Hirshfield addresses, essay by essay, the art, craft, and act of making poetry . . . These essays are both brilliantly ambitious--one random passage in her last piece, on 'writing and the threshold life, ' flows 14th-century Japanese poet Ono no Komachi (whose poems she has translated in the past) into Czeslaw Milosz into Emily Dickinson and Walt Whitman--and...