There are probably some people who wonder why I decided the world needed another vampire novel, let alone one about a bloodsucker who works for the president. But to me, changing the War on Terror to the War on Horror didn’t seem like that much of a leap. My vampire Nathaniel Cade even has his birth in U.S. history. I got the idea when reading a weird factoid about a sailor pardoned by President Andrew Johnson after being accused of killing two men and drinking their blood. I wondered: What would a man sitting in the Oval Office do with a vampire? Then it hit me. That was the wrong question. The right question is: What wouldn’t the president do with a vampire? Since 9/11, it seems that the United States has struggled with one nightmare after another. There’s a feeling that the ground isn’t stable under our feet; that it might crumble at any moment and the graves will open and all kinds of nasty, hungry things will spring out. You can see how we’re handling it in our hunger for stories of zombies and vampires and conspiracies. John Connolly‘s Charlie Parker is a detective constantly fighting ghosts and…