"Poetry," wrote Carl Sandburg in his Good Morning, America, "is a pack-sack of invisible keepsakes. Poetry is a sky dark with wild-duck migration. Poetry is the opening and closing of a door, leaving those who look through to guess about what is seen during a moment." For millions of Americans and readers around the world, Sandburg opened that magic door to poetry for perhaps the first time. Readers who might have otherwise never approached the carefully metered world of prosody eagerly consumed Sandburg poems, with their free verse incantations of the American quotidian. Sandburg's themes and language are those of the people, of the common man. He had, according to Kenneth Rexroth in his American Poetry in the Twentieth Century, "a perfect ear for the beautiful potentials of common speech, something he learned from folk song, but mostly he just learned it from listening." Sandburg indeed listened to...