The family of Mary Todd Lincoln, the president's wife, was a large one, and split down the middle by the Civil War, with members fighting on both sides—a fact that enabled Lincoln to empathize deeply with the war's ravages. Historian Stephen Berry from the University of North Carolina will tell the story, the first major study of the Todd family, in a book just bought by Houghton Mifflin's Eric Chinski from agent Andrew Wylie, North American rights.