Although both are credited to the same author Seth Grahame-Smith, the movie and its source novel are very different. Adam and Vadoma do not appear in the book - they were created to satisfy the fantasy-action movie tradition's demand an "archnemesis". In the book, Henry became a vampire in the 1580s and Abe recognizes him as such at first sight. Vampiric twists are given to many well-known trivial anecdotes from Abraham Lincoln's biography, as well as additional Civil War battles such as Bull Run and Antietam. There are tangential subplots involving historical figures such as Edgar Allan Poe, William Henry Seward, General George B. McClellan, and John Wilkes Booth. (The movie's inclusion of Harriet Tubman, who was not in the book, may attempt to compensate for this loss.) Mary Todd Lincoln never learns about vampires. Vampires are additionally able to kill other vampires, and there are many "vamp-on-vamp" battles whose absence is considered by book fans to be one of the film's largest shortcomings. There is also a surprising twist at the end, as well as a sequel novel.
