To date, J. K. Rowling’s books have been read by more than 350 million people. But her latest eagerly awaited offering - her farewell to the world of Harry Potter - will be enjoyed by only a tiny number of fans.

The boy wizard is a household name around the globe, and the books depicting his story have broken numerous sales records and made his creator the first ever billionaire author.

Now, Rowling has come up with what she described as a “wonderful way” to say goodbye to all things Hogwarts.

Four months after publishing Harry Potter and the Deathly Hallows, Rowling has created a limited edition volume of “wizarding fairytales” that relate to this final adventure.

Only seven copies of The Tales of Beedle the Bard, which gets a mention in the Deathly Hallows, will be produced.

Harry’s friend Hermione receives the book in the will of Albus Dumbledore, the headmaster at Hogwarts, “in the hope that she will find it entertaining and instructive”. Rowling has now brought it to life by personally crafting a 160-page, handwritten and illustrated volume.

The book contains such typically Rowlingesque characters as tree stumps with eyes and hairy hearts, and includes a frontispiece noting that the stories were “translated from the original runes”.

The seven copies are beautifully bound in brown morocco leather and decorated with designs in silver and moonstone, and are a must-have for the millions of diehard Potter fans desperate to discover the tales inside.

“Six of these books have been given to those most closely connected to the Harry Potter books during the last 17 years,” Rowling wrote in the book’s dedication. Whether they include Daniel Radcliffe, who plays Harry Potter in the films, or Christopher Little, the agent who discovered her when she was a penniless single mother living in Edinburgh in the early 1990s and struggling to find a publisher, remains to be revealed.

The seventh is to be auctioned by Sotheby’s in London next month to raise money for The Children’s Voice, a charity that she co-founded two years ago and which campaigns for children’s rights across Europe.

That copy has been read by nobody apart from the author, Sotheby’s said yesterday.

Dr Philip Errington, the auction house’s deputy director of books and manuscripts, said: “Only the person who buys it will be able to read it. It’s being kept secret.”

Of the five wizarding fairytales contained inside, only one - The Tale of the Three Brothers - is told in the final Harry Potter novel.

In The Tales of Beedle the Bard, Rowling tells the four remaining tales, which contain the clues that were to prove crucial to Harry Potter’s final mission to destroy Lord Voldemort’s Horcruxes.

Their titles - The Fountain of Fair Fortune, The Warlock’s Hairy Heart, The Tale of the Three Brothers, The Wizard and the Hopping Pot and Babbitty Rabbitty and her Cackling Stump - featured in the Harry Potter books before she thought of writing them, and the author said that it had been “a bit of a challenge” to write the stories to fit the title.

She said that the proceeds from the sale of the seventh copy, which will be auctioned on December 13, will be used by Children’s Voice “to help institutionalised children who are in desperate need of a voice”.

She added: “It’s a huge, silent scandal how many children within Europe are institutionalised - a child with mental health issues who has been taken from their family or given by the family to an institution and then placed in a cage.”

Harry Potter fans will be able to view The Tales when they are placed in a display case at Sotheby’s in London from December 9 until December 12, although whether they are offered more than a glimpse of the title page remains to be decided.

With the auctioneer estimating that the book will fetch at least £50,000, only one very lucky, and rich, bidder will be able to take the volume home.

The world record for a Potter first edition at auction was broken last month when a collector paid more than £27,000 at Bloomsbury Auctions in London for a signed copy of Harry Potter and the Philosopher’s Stone.

However, as Rowling has retained the publication rights to The Tales, it is not beyond the bounds of possiblity that their mysteries will one day be available to her young fans.

For now, Potter addicts will have to make do with a special auction catalogue, costing between £6 and £8. Proceeds from sales will also be donated to The Children’s Voice.

Times Recommends

• Superfreakonomics by Steven D Levitt and Stephen J Dubner
• The Times picks the 50 best paperbacks of 2009
• Vincent van Gogh’s letters show the soul of the artist