Supermarkets such as Asda and online retailer Amazon have joined traditional book stores in a fierce battle to attract millions of fans through their doors for the long-awaited launch of 'Harry Potter and the Half-Blood Prince'.

Multi-millionaire author J.K. (Joanne Katherine) Rowling is due to unveil the book at one minute past midnight on Saturday morning (2301 GMT Friday night) at a special ceremony in Edinburgh Castle, Scotland.

At the same time, thousands of other "Potter parties" will transform book shops across Britain into colourful scenes of jubilation as fans, many in fancy dress, scramble to get their hands on the first copies.

"The excitement in all our stores is really building up," said Sarah Hodson, a spokesperson for WH Smith, Britain's biggest book seller, which is opening hundreds of outlets for a night of wizards, live owls and fancy dress.

British firm Bloomsbury will publish the book in Britain, South Africa, New Zealand, Australia, Canada, Hong Kong and Singapore, while US publisher Scholastic will serve some 10.8 million copies up to the United States.

English-language versions of Potter's latest adventures at Hogwarts School of Witchcraft and Wizardry will also be available in other countries on the big day, with translated manuscripts due out in a few months.

"It is going to be the biggest thing ever," said Jon Howells, a spokesman for Ottakars, another of Britain's main book sellers.

"No other book really compares. People don't queue up at midnight for any other author, and they don't just do it in their thousands but in their tens of thousands, in their hundreds of thousands," he said.

Ottakars has changed its name to "Pottakars" for this week only to mark the launch, and is planning a series of ambitious parties at its stores, with 135 out of 137 of them opening for midnight.

Price war erupts

Howells said Rowlings' series had given an unprecedented boost to the book industry, encouraging more children and adults to read and also opening their eyes to a range of other, lesser-known, but similar writers.

"The whole profile of children's books has been raised since the Harry Potter thing started going. Publishers spend more money on them, they publish a lot more and they publish them better," he said.

But with book vendors preparing for record-breaking sales from the latest instalment, a price war has erupted in Britain as companies compete to pull in as many Potter fans — young and old — as possible.

Supermarkets and online retailers, with their low cost and high volume business model, have been able to undercut high street stores, offering the new book for as little as £8.96 (€13, $16) compared with £9.99 at WH Smith, £10.99 at Ottakars and £12.00 at rival Blackwell's.

Amazon.com has already taken 1.4 million pre-orders for the sixth chapter in Harry Potter's life, while Asda — the Wal-Mart-owned supermarket chain more known for bargain groceries than literature — said demand is huge.

"We are anticipating this to be our biggest-ever selling book," said company spokesperson Dominic Burch.

A spokesperson for Blackwell's said, however, that the price war was dashing any hopes of making a big profit out of Potter.

"You have got the supermarkets selling at virtual cost so (the book)... in terms of making money probably isn't very important," said Dawn Barnes. At the same time, she added: "In terms of good customer relations and having events to excite and interest the kids, and the fact that it promotes children's reading, it is very important."

AFP