Writer Terry Pratchett has poked fun at Harry Potter author JK Rowling for saying she did not realise she was writing a fantasy novel.
Terry Pratchett is the author of the best-selling Discworld series
He wrote to the Sunday Times:"I would have thought that the wizards, witches, trolls, unicorns, hidden worlds... would have given her a clue?"
Harry Potter and the Halfblood Prince has been a runaway bestseller in the UK and US since its release on 16 July.
Pratchett is one of the UK's most successful novelists.
His comments came on Rowling's 40th birthday, also Harry Potter's birthday.
In a recent interview with Time magazine, Rowling said she was "not a huge fan of fantasy" and was trying to "subvert" the genre.
The magazine also said Rowling reinvented fantasy fiction, which was previously stuck in "an idealised, romanticised, pseudofeudal world, where knights and ladies morris-dance to Greensleeves".
JK Rowling recently launched Harry Potter and the Half-Blood Prince
Pratchett, whose first fantasy novel was published 34 years ago and has since sold more than 40 million books, said in his letter that the genre had always been "edgy and inventive".
"Ever since The Lord of the Rings revitalised the genre, writers have played with it, reinvented it, subverted it and bent it to their times," he wrote.
"It has also contained some of the very best, most accessible writing for children, by writers who seldom get the acknowledgement they deserve."
His full response to Rowling's admission that she did not think Harry Potter was fantasy as she was writing it, was:
"I would have thought that the wizards, witches, trolls, unicorns, hidden worlds, jumping chocolate frogs, owl mail, magic food, ghosts, broomsticks and spells would have given her a clue?"
Meanwhile, Rowling celebrated her 40th birthday on Sunday, the day she has also made her young creation's birthday.
The author's website displayed pictures of a birthday cake and birthday card with the words: "Happy birthday Harry Potter."
Fans have been trying to deduce how old he is, with one site saying the boy wizard has now turned 25.