JK Rowling has said she is back at work, just days after her final Harry Potter book was published.
JK Rowling launched the last Harry Potter book in London
In an interview with the USA Today newspaper, the author said she was sad the Harry Potter series had come to an end, but would not stop writing.
"I'm sort of writing two things at the moment," she said. "One is for children and the other is not for children."
Eleven million copies of Harry Potter and the Deathly Hallows were sold in the first 24 hours of publication.
Warning: the remainder of this story may contain plot spoilers about Harry Potter and the Deathly Hallows.
Rowling, 41, said she expected to drop one of her two new books, which is what happened when she started writing Harry Potter and the Philospher's Stone in the 1990s.
"The weird thing is that this is exactly the way I started writing Harry," she said.
"I was writing two things simultaneously for a year before Harry took over. So one will oust the other in due course, and I'll know that's my next thing."
Fans around the world scrambled to get their hands on the book
Rowling admitted to being angered that the last of the seven-novel series had been posted on a website prior to the official release.
But she said she was heartened that rumoured endings included the death of the boy-wizard.
"I was very proud that people thought Harry's death was a genuine possibility. I wanted the reader to feel that anyone might die, as in life," she said.
Rowling added that she hoped the Harry Potter series would live on.
"Do I think they'll last? Honestly, yes," she said.
"In 50 years' time, if people are still reading them, they deserve to be read, and if they're not, then that's okay."
Some 325 million copies of the first six volumes have been sold worldwide, and the books have been translated into 64 languages.