In July 1863 the invading Army of Northern Virginia, confident from its victory at Chancellorsville, unexpectedly encountered the Army of the Potomac, still without a general Lincoln could trust, at a small town in Pennsylvania. And there, among the verdant hills, rich fields, and sparkling brooks around Gettysburg, the two armies slaughtered each other in fearful numbers. My Enemy, My Brother is a remarkable re-creation of that battle, told not as...