Between 2011 and 2015, the Opinion section of The New York Times published Disunion, a series marking the long string of anniversaries around the Civil War, the most destructive, and most defining, conflict in American history. The works were startling in their range and direction, some taking on major topics, like the Gettysburg Address and the Battle of Fredericksburg, while others tackled subjects whose seemingly incidental quality yielded unexpected riches and new angles. Some come from the country's leading historians; others from those for whom the war figured in private ways,...