While mildly entertaining, this book was also rather stupid, by which I mean the plot relied on stupidity of the characters and stupid contortions by the author to attribute historical events to vampires. The narrative itself was dizzying, essentially stories within a story within a story, and sometimes I lost track of the point of view.
The book opens with the story of Seth Grahame-Smith, a loser wannabe writer wasting away his life in a rural five-and-dime in upstate New York until a vampire drops Lincoln's secret journals in his lap and tells him to write the story.
Then it shifts into the story the fictional Seth Grahame-Smith wrote, which is a biography of Lincoln's life as a vampire hunter. He writes it in that distanced third-person used in historical biographies, frequently dropping in "excerpts" of Lincoln's journal, except sometimes the "excerpts" won't be from Lincoln's journal at all but will be the first-person narrative of some other person telling Lincoln a story and it's all sort of muddled and trying too hard, and there wasn't even much vampire slaying, IMO. There were a few times I considered just setting the book aside because I was bored.
Also — he sets up some drama with the fictional SG-S in his opening that is never resolved as he never comes back to SG-S's story in the end. That annoyed me.
Overall, I think I would have preferred a more straightforward narrative approach with Lincoln as a character and SG-S writing from his point-of-view than this faux biography.