Harry Potter author JK Rowling has written a novel for adults, which she said would be "very different" from her best-selling books about the boy wizard, her publishers announced on Thursday.
Publishers Little, Brown said they would release further details about the book, including the title and worldwide publishing date in print and electronic form, later in the year.
"Although I've enjoyed writing it every bit as much, my next book will be very different to the Harry Potter series," Rowling said in a statement.
The British writer has changed publishers for the project, leaving behind Bloomsbury, with whom she became the world's best-paid author.
"The freedom to explore new territory is a gift that Harry's success has brought me, and with that new territory it seemed a logical progression to have a new publisher," she said.
"I am delighted to have a second publishing home in Little, Brown, and a publishing team that will be a great partner in this new phase of my writing life."
Her new editor, David Shelley, said the publisher was "thrilled, honoured and proud" to be working with Rowling, adding that for him, it was a "personal and professional dream come true".
"She is one of the best storytellers in the world, and I am looking forward enormously to helping bring her new novel for adults to her fans and admirers, and to introducing her writing to new readers the world over," he said.
Little, Brown will publish the book in Britain and the United States, while Hachette will be the publisher in Australia and New Zealand.
Rowling laid down her pen -- and Harry's magic wand -- when she finished the seventh and final Potter book in 2007, which have sold more than 450 million copies around the world.
The books were made into eight films, with the last, Harry Potter and the Deathly Hallows: Part 2 making more than $1 billion last year.
Rowling is Britain's 15th-wealthiest woman, according to The Sunday Times newspaper's Rich List 2011, with a £530-million fortune.