Few events can stir up a scandal more than an autobiography of a First Lady's confidante. In 1868, a controversial tell-all called Behind the Scenes introduced readers to Elizabeth Hobbs Keckley. Mrs. Keckley was a former slave who had been Mary Todd Lincoln's dressmaker and friend during the White House years, and in the aftermath of President Lincoln's assassination. The book exposed Mary's marriage and her erratic behavior, along with confidential...