Life after Harry Potter: Can JK Rowling cast her spell over grown-ups too?

With pre-orders for her new novel topping one million, the author is set for another bestseller

Thursday’s release of JK Rowling’s new book is set to be the biggest publishing event of the year (PA)

JK Rowling's first novel for adults, which treads on very different ground to her bestselling Harry Potter series, is set to become a publishing sensation when it hits bookshelves next week.

Waterstones, the country's biggest book-chain store, revealed that the comic novel, The Casual Vacancy, has received the largest number of pre-order sales this year. This number is believed to be five figured, although online pre-orders have reportedly reached well over a million already. The RRP for the hardback is £20 but many outlets are reducing this considerably, with Waterstones pricing it at £10.

The secrecy, as well as the excitement, around Rowling's latest offering, has guaranteed its status as the biggest publishing event of the year. Waterstones is opening its doors an hour earlier than usual, at 8am, on its official publication date next Thursday. Until then, Rowling's publisher Little, Brown has stipulated that the books should not even appear on display. Staff will come in early to put out display copies and prepare for the crowds.

Jon Howells, a spokesman for Waterstones, described it as one of the first "Super Thursdays" leading up to Christmas, not least because Jamie Oliver was also publishing his book, 15-Minute Meals, on the same day.

Mr Howells said that while he anticipated a big rush at the outset, the book would, in all likelihood, not inspire the equivalent of Pottermania.

"Certainly, the anticipation for JK Rowling's book has been great because it's the first non-Harry Potter book and it is for a purely adult audience. I think it will see a fantastic level of first day and first weekend sales and after that people will come to it more steadily.

"We are treating it as a very different thing from the Harry Potter books. The way readers will approach this will be different.

"A lot of the readers will be curious and interested in what this book can do for them. There was a huge sense of urgency with the Harry Potter books, and people wanted to read them quickly so that they would not find out the plot through other mediums, while this is a standalone story," he said.

A spokeswoman for Tesco, which will also be stocking the book, said: "If the hits on the Tesco Books blog are anything to go by, we think it could be one of our bestselling books in the run-up to Christmas."

The plot of the book, which revolves around the inhabitants of a small English town, has been fiercely guarded, and newspaper reviewers have been asked to sign the kind of long and stiffly worded pre-publication confidentiality contracts that a celebrity footballer might use to protect his darkest secrets. A limited number of copies will be delivered by hand to reviewers' homes today.

Rowling is due to attend her only question-and-answer session in front of a live audience in London on the day of publication. The event, at the 900-seat Queen Elizabeth Hall in the Southbank Centre, sold out within 48 hours and will also be attended by the world's media. The Southbank Centre condemned the selling of single £12 tickets on eBay for £65 each. The event, which will last just under two hours including a 30-minute Q&A with the audience, will be transmitted in a live feed on YouTube.

Rowling will sign books afterwards, and audience members are limited to a one copy per person. Next month she will appear at the Cheltenham Literary Festival and sign copies there.

Little, Brown refused to reveal the numbers of copies that have been printed so far – but the book is expected to sell millions.