BOSTON —The American Library Association selects “The Sympathizer,” by Viet Thanh Nguyen, published by Grove Press, an imprint of Grove Atlantic, as the winner of the 2016 Andrew Carnegie Medal for Excellence in Fiction, and “Hold Still: A Memoir with Photographs,” by Sally Mann, published by Little, Brown, and Company, Hachette Book Group, as the winner of the 2016 Andrew Carnegie Medal for Excellence in Nonfiction.