Oates is a professional biographer and historian whose body of work focuses on American history from the Civil War, antebellum, and Western expansion periods. He is dedicated to the idea that biographies can be both factual histories, and important pieces of literature. He gives the reader insight on Lincoln the man, not the President, during the atrocities of the Civil War. He has an obvious regard for the President, taking time to meticulously explain Lincoln's political and personal moves: the whens, wheres, whys, and hows of Lincoln's life.