October 8, 2015 7:02 AM EDT

The Goosebumps Books by R.L. Stine are a ubiquitous series of playful middle-grade horror novels that have sold over 400 million copies worldwide. Since the series launched in 1992, it has also become a TV show and a video game, and if you’d asked me I would have guessed offhand that there were probably already half a dozen Goosebumps movies.

But in fact Goosebumps, starring Jack Black and opening Oct. 16, is the first one. “We’ve had movie contracts for like 20 years,” says Stine, who is 72 and lives in New York City and who I also wouldn’t have guessed was a real person. “Twenty years ago Tim Burton was supposed to be the producer, but no one could ever come up with a script that anyone liked. Because everyone was just thinking, ‘Which book should we do?’ And then finally somebody came up with this idea and said, ‘Well, let’s do all of them. Let’s take all the monsters, and make R.L. Stine the main character, and have him worried because all his monsters are escaping.'”

And that’s what they did: in the movie all the monsters in the books turn out to be real, and they escape from the books, and Stine (played by Black) and two good-looking teenagers have to put them back in again. Stine didn’t write the screenplay himself. “No one asked me,” he says. “No one wants the author!” Stine, who is one of the most spontaneously funny people I’ve ever met, has a way of adopting a slightly woebegone persona while at the same time somehow letting on that he knows he’s not fooling anybody.

He was born Robert Lawrence Stine in Columbus, Ohio, in 1943. His father worked for a restaurant-supply company. His mother kept house. Stine knew early on what he wanted to be. “I never give writing advice,” he says. “I think people who are going to be writers are like me, they knew it very young. When I was 9, I knew I wanted to be a writer. You don’t have to tell these people, ‘Read a lot’ or ‘Write something every day.’ They’re already driven to do it.”

Stine was driven, but success wasn’t immediate. His first job as a writer was working for a woman who published six different movie magazines from a brownstone on 95th Street in New York City. His job was fabricating interviews with movie stars. “I would come in in the morning and she would say, ‘Do an interview with Diana Ross.’ And I would sit down and write an interview with Diana Ross. And she would say, ‘Do an interview with Tom Jones–the rumors about him aren’t true!’ And I’d just make it up! And she’d say, ‘Do another one–the rumors are true!’ So I learned how to write really fast and how to make stuff up.” The skills have come in handy. (These stories and many more can be found in Stine’s highly readable autobiography It Came from Ohio!, which is not to be confused with the 30th book in the Goosebumps series, It Came from Beneath the Sink!)

The Stine of the movie, who is creepy and mysterious, has very little to do with the real-life Stine, who is warm and charming, but Stine does make a cameo. Watch for him at the very end: Jack Black is walking down a school hallway with a student, and Stine (the real Stine) walks by holding a briefcase and says, “Hello, Mr. Stine.” Black replies: “Hello, Mr. Black.” Then he explains to the student that Mr. Black is the new drama teacher. “I’m on for like four seconds,” Stine says. “Not even five. Four. They shot it 25 times. I said, ‘Jack, I would kill myself. I couldn’t work like this for anything.'”

Stine suggested that Black say he’s the new custodian instead, and they shot a few takes that way, but the change didn’t make it into the film. “It’s better, right?” Stine says. “They don’t listen to me.” In truth he doesn’t seem that tempted by Hollywood. “It’s total collaboration, if you like that. I kind of like sitting in a room and, you know, writing what I want to write.”

Right now he wants to write more Fear Street novels, a young-adult series that has been dormant for 20 years. He’ll write six in the next year or so. “A new one came out yesterday, it’s called The Lost Girl,” he says, “and it has the most gruesome scene in it that I’ve ever written, involving horses. It’s a really horrible scene, horrible. I should be ashamed.”

Some things have changed since the last time Stine wrote young-adult fiction, not least the state of consumer technology. “The cell phone has ruined more plots than anything,” he says. “Before, you could do a book where a girl is getting these frightening phone calls. Who’s calling me? Who is it? Now she looks at her phone. She knows who it is. And the book is over.” But other things remain constant. “The fears don’t change,” Stine says. “Most of these books could have been written when I was a kid. Horror doesn’t change.”

This appears in the October 19, 2015 issue of TIME.

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