Winners of the 2004 Ambassador Book Awards   American Studies: They Marched into Sunlight, David Maraniss; Simon & Schuster Biography & Autobiography: Hawthorne , A Life , Brenda Wineapple; Knopf Fiction: The Time of Our Singing, Richard Powers; Farrar, Straus & Giroux Poetry: Robert Lowell: Collected Poems, edited by Frank Bidart & David Gewanter; Farrar, Straus & Giroux Distinguished Achievement Award Robert A. Caro