Rowling has an agreement with Little, Brown in the United States and Britain to release her first adult novel, publishers announced on Thursday. Little, Brown also published the massively popular "Twilight" series.
The title, release date and details about the long-rumored book were not announced. But Rowling's neighbor in Edinburgh, author Ian Rankin, said on Twitter on Thursday that he thinks the book will be a mystery novel.
"Wouldn't it be funny if J.K. Rowling's first novel for adults turned out to be a crime story set in Edinburgh?" Rankin wrote. "My word yes."
Rowling's seventh and final Potter story came out in 2007. Since then, the famed author has said that she was working on an adult book and on a Potter encyclopedia.
Her agent, Neil Blair, would not disclose financial details of the deal but said there had been no auction.
Rowling's novel will be available in both print and electronic formats.
The Associated Press contributed to this report.