Harry Potter author J.K. Rowling's first foray into adult fiction hits shelves on Sept 27.

The Casual Vacancy features a large black "X" on its cover, which appears to be a box on a ballot paper set against a bright yellow and red background, her publishers Little, Brown revealed recently.

The 512-page book is "a big novel about a small town".

Set in a seemingly idyllic English town called Pagford, it centers around an election to the parish council following the shock death of Barry Fairbrother in his early 40s.

Publishers previously promised a "blackly comic, thought-provoking and constantly surprising" story.

Since her seven Harry Potter novels became a global publishing phenomenon, selling an estimated 450 million copies, Rowling's every move is followed closely by the industry.

Rowling is also working on a Harry Potter encyclopedia and will donate proceeds from its sale to charity. It is unlikely to appear any time soon, however, as the author says it is a "time-consuming job".

- Reuters