The author, who relaunched her official website this afternoon, confirmed that she was working on a story "very different" to the Harry Potter series earlier this year.
Published by Little, Brown and Company, The Casual Vacancy will be Rowling's first tale for adults
In the publication announcement, the first details of the book's plot were confirmed.
"Rich at war with poor, teenagers at war with their parents, wives at war with their husbands, teachers at war with their pupils... Pagford is not what it first seems.
"And the empty seat left by Barry on the parish council soon becomes the catalyst for the biggest war the town has yet seen. Who will triumph in an election fraught with passion, duplicity and unexpected revelations?"
The book will be published worldwide in the English language on e-book, unabridged audio download and CD on Thursday, September 27.