Fox News host Bill O'Reilly has never shied away from controversy. This time it is the commentator's new history book, "Killing Lincoln," that's in the eye of the storm. A reviewer for the National Park Service's bookstore at Ford's Theatre has recommended that the store pull the book due to "lack of documentation" and "factual errors." O'Reilly responded to his critics on his show. (Video after the jump.) Kenneth C. Davis, author of the "Don't Know Much About History" series of books, discusses the factual accuracy of O'Reilly's book. Davis is currently working on a new book, "Don't Know Much About Presidents."