Just how original is JK Rowling? The thousands of children who queued up at bookshops around the country on Friday night and are now happily reading Rowling’s sixth offering, Harry Potter and the Half-Blood Prince, don’t care: they just love a great story.

But two years ago, when the Booker-winning AS Byatt attacked Rowling’s “ersatz magic” in The New York Times as “a secondary secondary world, made up from intelligently patchworked derivative motifs from all sorts of children’s literature, from the jolly-hockey-sticks school story to Roald Dahl . . .” there were many in the literary world rubbing their hands with glee.

One reason for this is simple envy. While Rowling’s success has given her a fortune put at £500m in The Sunday Times Rich List, most children’s authors earn less than the minimum wage (£8,827). As the children’s author Mary Hoffman notes drily: “Most of us aren’t Rowling in it.”

Few have gone as far as one writer, who sued Rowling (unsuccessfully) for supposedly plagiarising the word “muggle”, but many, like Anthony Holden, one of the judges of the Whitbread who rejected the Prisoner of Azkaban for the prize, have heaped contempt on her.

Unlike Philip Pullman, who modestly acknowledged the many influences upon His Dark Materials, Rowling has named only three children’s writers — CS Lewis, Tolkien and Elizabeth Goudge — as influences, all of whom are dead. Yet there are numerous living authors whose conceptions predate the publication of Harry’s first adventure and at least underline the tradition out of which her world grew.

Take the idea of a school for wizards. In 1968 Ursula le Guin published A Wizard of Earthsea, whose young hero, Ged, travels to the island of Roke to learn how to control the magic powers he was born with. A silver-haired, kindly old Archimage gives his life to protect Ged (as many suspect Dumbledore will eventually do for Harry) when an evil monster is released on the world, scarring our hero’s face.

Equally, Jill Murphy’s much-loved Worst Witch series is set in a boarding school (Miss Cackle’s Academy for Witches). But though Mildred, the Worst Witch, like Harry Potter, gets into scrapes with bullies and teachers, there is never a twinge of real terror in Murphy’s imaginary world. Harry Potter experiences not only the ordinary trials and triumphs of the boarding-school genre, but repeated attempts to murder him.

If he is an orphan, like Frodo Baggins and Luke Skywalker, and cursed with a monstrous adoptive family reminiscent of Roald Dahl’s Matilda, he is also asked to solve a series of dangerous puzzles that are unlike anything else in children’s literature.

“Shakespeare didn’t worry about pinching plots,” observes Elizabeth Kay, the bestselling author of the Divide trilogy, who is leading a creative writing workshop at a conference on Rowling’s work at Reading University this week. “Writers are frequently accused of plagiarism when they are simply going back to the same source materials.”

Kay’s point about Shakespeare is a good one, for while our modern conception of genius makes creativity synonymous with originality, this has not always been the case. Our greatest author was admired by his contemporaries for the “lively tuning” of familiar material.

Diana Wynne Jones, author of the Chrestomanci series, probably comes closest to Rowling in treating magic as a source of humour, but her characters do not have to grapple with celebrity, which Harry, unlike any other hero, is born into; and they do not have to return to an ordinary world of obscurity and oppression at the end of every school year.

“Harry is similar to previous literary heroes because he strives to do good and must go on a quest to fulfil his goals, yet he is also original because unlike traditional fairy tales Harry’s ultimate goal is not marriage or enthronement but knowledge and self-identity,” says Giuliana Peresso, lecturer at Newcastle upon Tyne University, who is presenting a paper at the Reading conference. “One of Harry’s greatest discoveries, similar to Ged’s in A Wizard of Earthsea, is that who he is isn’t nearly as important as what he chooses to do with his powers.”

This is similar to Luke Skywalker’s decision on how to use the Force, but the arena in which his decisions are made is as discrete as that of Narnia. Alternative, secret worlds in which magic happens are as old as Celtic myth and if JM Barrie’s Peter Pan was the first to bring children into it, the idea of one coexisting, unnoticed, with our own is even closer in the works of Eva Ibbotson, whose book, The Secret of Platform 13, even has a platform at King’s Cross as being the entrance to it — just like Platform 9¾ for the Hogwarts Express.

But where Rowling has used traditional fairy-tale creatures, she has put her own spin on them. Fairies and sprites are not pretty, benign wish-granters but domestic pests; owls are not familiars but postmen. For every dragon and unicorn there are invented creatures like Thestrals (skeletal horses visible only to those who have seen death), Blast-Ended Skrewts (don’t ask) and, of course, the Dementors.

Nobody else thought of Floo powder or Quidditch matches. Nobody thought of a Sorting Hat, which sorts out pupils into their respective school houses according to temperament and ability, or wands that choose their owner.

These are far from being characteristic of a “secondary secondary world”, as Byatt claimed. Harry Potter’s creator has simply thought of the logical consequences to certain people having magical abilities and imagined how the world would cope with them.

Those who are enjoying a weekend of total tranquillity may at least be grateful for that.