Abraham Lincoln: Vampire Hunter.
Yep, you heard that right. The title of this book (however strange and shocking) lays it all out on the line for us. It tells us exactly what the author's up to: let's take Abraham Lincoln and imagine a world where he is a vampire hunter, without changing too much of his actual history. Abe's mom still dies, he becomes president, he fights the Civil War—except we learn that there are vampires connected with all of this history.
Plus, the form of the title follows a formula that is pretty common with biographical and historical works. The formula is NAME + Colon + SOMETHING ELSE.
For examples, there's Walter Isaacson's Benjamin Franklin: An American Life; Paul Nagel's John Quincy Adams: A Public Life, A Private Life; and Ron Chernow's Washington: A Life; and many more.
Sure, this book has a wild premise (Lincoln + vampires). But at least Seth Grahame-Smith is being up front about it. And he gives the book a nice dose of authenticity by slapping a title on it that smacks of a common biography formula. Think of it as deadpan humor.
Check out the possibilities: he could've named this "Abraham Lincoln: Freedom Fighter" but that wouldn't have told the reader how wild the premise is. Or he could've titled it, "The Wild Adventures of Bloody Abe and his Vampire-Hunting Ax"—but that might've made it sound too wild and less serious. He has to walk a fine line, and walk it he does.