She wasn’t saying it to be mean or anything, Justin Cronin’s daughter Iris assured him, but it was time to face facts: Those earnest literary novels he was writing were boring, no matter how many prizes they were winning. He needed to jazz things up.

“She was a little worried about me,” Cronin recalls. “I said, ‘OK, what you want me to write about?’ ‘Vampires,’ she said. And now here we are. I’ve essentially written 2,000 pages on a dare from an 8-year-old.”

A pretty good dare to take, as it turns out. Cronin’s vampire-apocalypse trilogy that began with The Passage and The Twelve (with the final book, The City of Mirrors, expected in 2014) has already earned him something north of $5.5 million in royalties and movie-rights sales. Critics love them. Fans are nuts for them.

Even Stephen King, whose last foray into commentary on fangbanger lit was an acid observation that Twilight author Stephanie Meyer “can’t write worth a damn,” was smitten. “You put the scare back in vampires, buddy!” he applauded during a phone call to Good Morning America, where Cronin was being interviewed.

Iris, now 15, got the peace of mind that comes with knowing your dad won’t have to live under a bridge. Oh, and also a pony. But she and her brother Atticus, 9, remain severe critics. “My kids still don’t care that I’m a writer,” Cronin sighs.

Or, as his Twitter account bio calls him, “author of long books in which many people die.” The narrative that stretches through The Passage and The Twelve starts in the not-terribly-distant future, where a military-scientific expedition deep into the Bolivian jungle encounters a voracious flock of bats carrying a deadly virus that gives its victims herculean strength and an unquenchable thirst for blood. Hints in the text suggest that the book ends a thousand years later, with a rebuilt civilization trying to figure out what happened.

In between, the plague victims run amok, sleeping by day and ravaging the tattered remnants of humanity by night. They can be killed only by a bullet or stake through the thymus, an organ not far from the heart. In short, they sure sound like vampires, but oddly the V-word never appears.

In part that’s because Cronin doesn’t really consider his books vampire novels. When he wrote them, he was thinking not of Dracula or Salem’s Lot but the paranoid Cold War novels of the 1950s in which warfare reduced the Earth to a barely populated ash heap.

“I grew up during the Cold War, and I read all the classics of Cold War fiction,” says Cronin, 50. “The genre that drew me in most was apocalyptic fiction — not only nuclear war but biological war, especially some kind of creation story. Nevil Shute’s On the Beach. George Stewart’s Earth Abides, Pat Frank’s Alas, Babylon. And I was a huge fan of the Planet of the Apes movies, even the later ones that all looked like they were shot on a parking ramp.

“I was fairly convinced that before I reached the age of majority, I would probably be incinerated in a nuclear blast. It was a kind of psychological balm, I guess, but it turned into a lasting interest of mine.”

And midway through The Passage, as the bedraggled band of survivors at the center of his story encountered a colony of vampire collaborators, Cronin realized he was unconsciously being influenced by another source: George Orwell’s 1984, the subject of Cronin’s college thesis.