Mrs. Lincoln's Dressmaker by Jennifer Chiaverini

Mrs. Lincoln's Dressmaker: A Novel - Mary Todd Lincoln's dressmaker, Elizabeth Hobbs Keckley was born a slave.  Because of her sewing skills, she was able to buy her and her son's freedom.  As her reputation grew, she became the dressmaker for many of Washington, DC's elite.  This included Mrs. Jefferson Davis and Mrs. Robert E. Lee.  After Mrs. Lincoln chose her to make her First Lady gowns, Elizabeth not only became her modiste, but also her confidante and friend.

This novel is written from Elizabeth's point of view and covers the period from right before President Lincoln took office, through his assassination and Mrs. Lincoln's trials following her departure from the White House, to the period when Elizabeth wrote her memoirs and the aftermath that followed.