20130921-153822.jpg Justin Cronin at the festival (Ron Charles/THE WASHINGTON POST)

Former English professor-turned-vampire novelist Justin Cronin entertained a full tent of his thriller fans this afternoon at the 13th annual National Book Festival on the Mall.

He began by recounting the legendary story of how his daughter prodded him to stop writing “boring” novels and write something exciting instead. (To be fair, he’d won a PEN/Hemingway and a Whiting Award.)

He and his 8-year-old daughter started making up details. Their only rule was that everything they thought up had to be interesting. Soon, he had a multimillion-dollar movie/publishing deal.

The Passage,” the first book of his vampire trilogy, was a fantastic bestseller.

“You’re probably wondering,” he said, “what did I do to compensate my daughter for her contribution?”

“Well, I sent her to college, which I had no idea how I was going to do before . . . and I bought her a pony.”

In addition to finding a much larger audience, he found different readers, too. “Much to my delight, I have a number of readers in the military,” he said. A friend in the service told him, “Books are to deployment what cigarettes are to prison.”

The very cool, military storylines probably help, too. Cronin said he didn’t know much about guns before he started, but his dentist was willing to act as his tutor.

Cronin revealed that after he publishes the final volume of The Passage trilogy in two years, he’d like to bring out a fourth book that includes all the loose ends and stray stories that he couldn’t get in the series.

So keep the lights on.