The dynamic evolution of W.S. Merwin's verse -- allied with his accomplishments as translator, essayist and environmentalist -- have made him the most admired and imitated of American poets. He published his first volume of verse at age 24 and soon won acclaim for an impressive mastery of classical verse technique, combined with a vivid appreciation of animal life and the natural world. Merwin embraced the use of more colloquial language and contemporary themes in the 1960s, advocating experimentation in his influential essay, "On Open Form." When his book, The Carrier of Ladders,...