"I think it very likely that the next thing I publish will be for kids. I have a children's book that I really like, it's for slightly younger children than the Potter books," Rowling told the BBC in a television interview broadcast on Wednesday.
In one of a handful of appearances to promote "The Casual Vacancy," which hits bookstores worldwide on Thursday, Rowling told the BBC: "Truly, where Harry's story is concerned, I'm done.
Yet the 47-year-old best-selling British author did not rule out a Potter spin-off, while she was adamant it would never be for commercial reasons. The seven "Harry Potter" books have sold more than 450 million books worldwide.
"I have always left the door ajar because I'm not that cruel. If I had a fabulous idea that came out of that world, because I loved writing it, I would do it," she told the BBC.
"But I've got to have a great idea, I don't want to go mechanically into that world and pick up odds and ends and glue them together and say 'Here we go, we can sell this'. It would make a mockery of what those books were to me."
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Were that great idea to come, she said: "I probably would do it. I'm very averse to the prequel/sequel idea. I've never seen it work well in either literature or film. That's a personal preference."
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Rowling, who started her writing career as a financially struggling, single mother, said while there was clearly "an appetite for eight, nine, ten," Potter novels, she knew she only had enough plot for seven books about Harry's magical adventures.
Harry Potter books displayed at a bookstore in Beijing. Photo: Reuters/David Gray/Files
"To go further would have been money for old rope. Couldn't do it. And that's largely why I slapped on that epilogue (in the final "Harry Potter" novel). (It) says he's leading a quiet life, and he's earned it. He's done," she said of the boy wizard.
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Rowling said she would have liked more time to work on some of the books.
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"I had to write on the run and there were times when it was really tough. And I read them, and I think 'Oh God, maybe I'll go back and do a director's cut". I don't know," she said in BBC interview.
"But you know what?" she added. "I'm proud I was writing under the conditions under which I was writing. No one will ever know how tough it was at times."
Author J.K. Rowling with the cast of Harry Potter. Photo: Reuters
In a separate interview with ABC's "Nightline", Rowling revealed that she had signs of obsessive-compulsive behavior when she was a teenager, and that one of the characters in "The Casual Vacancy" was drawn from her own experiences.
"These are things I know from the inside," she said in the interview, some of which was aired on "Good Morning America" on Wednesday. "When I was in my teens, I had issues with OCD ... checking things, it's very common, double checking, triple checking, it's an anxiety disorder."
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Rowling has spoken openly in the past about dealing with depression, which she estimated she had not had to deal with for more than a decade.
She credited Harry Potter with helping. "Forget the money," she said; it gave her self-respect. "Harry gave me a job that I loved to do more than anything else," she told ABC.