J.K. Rowling is ditching the world of teenage wizardry to pen a new book for adults that will be "very different" from her "Harry Potter" series.

Rowling signed a deal with Little, Brown's British and U.S. divisions to release her first adult book. Although the title, release date and details about the book have been oft-rumored, nothing official has been provided.

Still, that didn't keep Rowling's Edinburgh neighbor, author Ian Rankin, from tweeting he believed Rowling has written a mystery novel.

"Wouldn't it be funny if JK Rowling's first novel for adults turned out to be a crime story set in Edinburgh?" Rankin wrote. "My word yes."

Rowling's agent, Neil Blair, said she would remain with Bloomsbury in Britain for the Potter books. Rowling's seventh and final Potter story came out in 2007.

"Although I've enjoyed writing it every bit as much, my next book will be very different to the Harry Potter series, which has been published so brilliantly by Bloomsbury and my other publishers around the world," the 46-year-old author said in a statement Thursday.

"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."

Rowling's Potter series about a boy wizard was published between 1997 and 2007 and broke sales records worldwide. The series has sold more than 450 million copies and been translated into 74 languages. The tales were turned into eight blockbuster films starring Daniel Radcliffe and culminated with last year's "Harry Potter and the Deathly Hallows: Part 2."

The Potter brand is estimated to be worth $15 billion by trade publication Advertising Age, while Forbes estimates Rowling is worth well over $1 billion.

Little, Brown publisher David Shelly said in a statement, "For me, quite simply, it is a personal and professional dream come true to be working with J.K. Rowling. 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." 

Rowling will now share a publisher with Stephenie Meyer of "Twilight" fame, whose books filled a void left after the Potter series ended.

Rowling's agent said the choice of a new publisher of her adult work was simple, "As her new book is for a different audience, and marks a new literary direction for her, it made sense to separate the two and for her new book to be launched by a different publisher."

Bloomsbury said its 15-year relationship with Rowling "remains stronger than ever" and new illustrated editions of Potter are on the way.

"We are pleased to announce that as part of our long-term strategy for Harry Potter we intend to publish illustrated editions of all seven Harry Potter books in a rolling program from 2013 onwards in addition to our partnership on e-books with the Pottermore Web site," the publisher said in a statement.

In the U.S., Scholastic noted it doesn't publish adult books but said it would continue to publish Rowling's children's books in North America.

Other authors who have successfully made the transition from writing for young people to adults include E.B. White and Sherman Alexie, while some like Ann Brashares ("Sisterhood of the Traveling Pants" series) and Daniel Handler ("Lemony Snicket") were less successful.

Contributed by International Business Times