The last instalment in the saga, Harry Potter and the Deathly Hallows, goes on sale at midnight.

Stores will stay open into the early hours to cope with the Potter frenzy.

And fans will be faced with the choice of whether to read the book from beginning to end - or turn straight to the final pages to discover whether schoolboy wizard Harry lives or dies.

Author JK Rowling has revealed that some characters meet a bloody end but their identity remains top secret.

Fans from all over Europe have been queuing outside Waterstone's in London's Piccadilly for three days to be certain of getting their hands on a copy.

Buyers will also be flocking to Asda after the supermarket announced last night it would be selling its 500,000 copies for just £5, £12.99 below the recommended retail price.

Sales will be limited to just two per person to prevent bulk-buying in what Asda describes as "the biggest book launch we've ever seen".

>> See our special countdown clock to the big moment.

Tesco will also be selling the book for £5 to anyone who spends £50 in one of its stores. Its normal price is £10.

Woolworths has cut its price to £6.99 for all customers who spend £10 or more in-store on Saturday and Sunday. Customers will be limited to one book purchase per transaction.

Rowling will give a moonlight book signing and read excerpts at London's Natural History Museum.

The event will begin at midnight and last until dawn.

It promises to be an emotional occasion for Rowling, who has confessed that she broke down and "absolutely howled" when writing the seventh and final book.

Some people already know more than they should about Harry's fate.

The New York Times published the first Deathly Hallows review yesterday - to the fury of Rowling and her publishers. A review also appeared in the Baltimore Sun.

Neither gave away which characters are killed off, but Rowling said she was "staggered'' that US newspapers had broken the midnight embargo "in complete disregard of the wishes of literally millions of readers, particularly children, who wanted to reach Harry's final destination by themselves, in their own time".

The New York Times described the final Harry adventure as a "monumental, spellbinding epic'' and said it ended with a "big-screen, heart-racing, bone-chilling confrontation".

It is 10 years since the first book, Harry Potter and the Philosopher's Stone, introduced us to Hogwarts School of Witchcraft and Wizardry.

Since then the books have sold 325 million copies worldwide, been translated into 64 languages and spawned five blockbuster films.

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