Many of Britain's leading booksellers are offering pre-ordered copies of Harry Potter And The Half-Blood Prince for almost half-price, sacrificing millions of pounds in profits.
While the recommended price is £16.99, many companies are offering the title for £8.99, making the hardback edition only marginally more expensive than the paperback when it is published next year.
Retailer Waterstone's is predicting the book will sell a colossal two million copies in the UK within 24 hours of the release, in the early hours of Saturday morning. It will eclipse the previous record for Order Of The Phoenix which sold 1.7 million in a day, and a further two million will be sold within 12 months, book experts predict.
"Normally a popular or much anticipated book would be lucky to sell 2 million copies in its lifetime, let alone its first 24 hours," said Waterstone's children's manager, George Grey.
Many stores - particularly supermarkets - are regarding the book as a loss leader, and smaller sellers who try to compete will struggle to make a profit. "We won't make a penny out of it," said one bookseller.
Hundreds of bookshops around the UK will open at midnight to handle the release of JK Rowling's penultimate volume in the Potter series, the largest launch in literary history. The hysteria will be repeated around the world, with simultaneous releases taking place in the US, Canada, Australia, New Zealand and South Africa.
The first five Harry Potter books have now sold more than 265 million copies in eight years, translated into 62 languages, and have generated an estimated fortune of £500 million for Rowling.
The author herself will be at the main launch event which is taking place in Edinburgh Castle during the witching hour on Saturday morning, where she will read from the book the moment it is published, to a hall full of specially chosen children, many of them competition winners. The room will be decked out to resemble Hogwarts school from the books and Rowling will emerge from a wooden panel.
A new report released today has also shown the importance of the Potter series in enhancing literacy among children. Three-fifths of children in the study, commissioned by Waterstone's, said that the tales of the boy wizard had helped improve their reading.
When Pottermania was in its infancy, many turned on the series for encouraging an interest in the occult, but researchers at Saint Joseph College, Connecticut, have now found the fantasies cast a positive spell on children.
They said a four-year study, Harry Potter: Are Children and Adults Reading the Same Books?, which is about to be published, dispelled the myth that Harry Potter novels confused children about magic and led them to the dark arts.
Dr Elizabeth Vozzola said: "The Harry Potter novels teach lessons of courage and friendship - not black magic."
Rowling's five previous books are the best-selling children's books in the UK since 1998, and the success has rolled out across the film industry. The first three films in the series have taken £1.35bn at the worldwide box office and, by the time the seventh film is released later this year, that figure is expected to rise to £3bn.Reuse content