"Laughter is the language of the soul," Pablo Neruda said. Among the most lasting voices of the most tumultuous (in his own words, "the saddest") century, a witness and a chronicler of its most decisive events, he is the author of more than thirty-five books of poetry and one of Latin America's most revered writers, the emblem of the engaged poet, an artist whose heart, always with the people, is literally consumed by passion. His work, oscillating...