ORPHAN boy is taken in by hostile relations and endures years of misery, often harshly neglected in favour of his relatives' natural child, before finally escaping for a life of adventure.

The plot of countless children's books, many of which have become well-loved favourites for generations of young readers.

But this simple storyline is also the starting point for what has become a publishing phenomenon, far outstripping its rivals, with more than 100 million copies sold worldwide, and the first in the series translated into 47 languages and sold in 200 countries. And now its success is likely to be magnified many times, with the imminent opening of Harry Potter and the Philosopher's Stone, the first film in a planned series of seven.

Few bestseller lists are complete without a Harry Potter title or four, but what sets JK Rowling apart from her contemporaries is that her books dominate, not just the children's fiction charts, but also the adult ones as well. Few authors have been able to reach such a wide readership, but JK Rowling's feat has been not only to get people to read her books, but also to inspire the sort of devotion which has parents waiting as eagerly as their children for the next instalment.

But while the basic formula might be easy enough, if it was that easy everyone would be doing it, and there is no doubt that Rowling has added a magic ingredient of her own, according to Dr Michael Anderson, of Newcastle University's Centre for Family Studies.

"I think what is exciting in those books - and I've scanned them myself - is the creativity of the author. That is what appeals to adults," he says. "I do a lot of training and development in creativity and one of the references I give is The Philosopher's Stone. To me, it is like creative alchemy - you take a very simple, basic and modern idea, and turn it into something magical and fantastic.

"JK Rowling has taken some basic ideas of children's literature and put them together with a whole new universe of ideas that adults have discarded as fanciful, and rediscovered them in a new way."

Magic features heavily in many children's fantasies, so the story of a young boy entering a magical world has a strong appeal. "Some of the research I have done is on how children have magical friends. These friends don't exist physically, but they exist in the minds of the children, and that is thought by psychologists to be a very healthy thing," he says.

"The other main ingredient is this world of disappearing and reappearing, of flashing lights and fire and wizardry, the things that children are attracted to. They don't see them in their ordinary lives, but they're very happy to entertain them. And that is also why it is attractive to adults. It is recreating that world of mysticism and magical friends. It is nostalgia for their childhood, and, because it is set in an earlier period, it is also nostalgia for the past.

"There is also the issue of hype. Ever since someone said this author has sold lots and lots of books, it has taken on a momentum and become a phenomenon, but that leaves unexplained why the books are so appealing."

It is here, he suggests, that Rowling might have an unlikely parallel with another children's favourite, Enid Blyton. Although there was nothing fanciful about her stories, there is a common thread.

"There is a riddle to be solved. If readers know there is an answer, and they have to get to it, that makes it exciting and interesting. And it is probably more true of adults, than of children, that they want a story. It may have been targeted at a specific market, of nine to 13-year-olds, but most of the purchases are by adults for themselves."

The importance of a strong story to Harry Potter's wide appeal is a key feature, according to Dr Liz Todd, a child psychologist at Newcastle University, who is also director of the university's educational psychology and education department. "Harry Potter is an excellent story. It is an excellent narrative, with depth of characters and it has the kind of fantasy element that always does seem to appeal to adults and children," she says. "It doesn't talk down to children, so adults don't feel excluded.

"There are lots of examples of similar kinds of narratives, but I think this has an added element, and that is it's continually surprising and in such detail. The picture that speaks and lets you into the upstairs room, the owls that carry things - there is a continual detail of surprising things, and adults as well can be continually surprised.

"It could have out-video gamed children, and if you have managed to create that in a text that is quite extraordinary. It is the same kind of suspense - a child isn't playing the book to win but you are continually kept wondering what is going to happen."

She says the classic plots of wicked stepmothers and children going off for adventures on their own, without the need for adults, might appeal to some basic insecurities, as well as dreams of escape, within all of us. "There is an element of being taken back to your childhood and reliving these kind of fantasy stories."

She says while the book doesn't challenge gender stereotypes, with a lack of strong female characters, this may be more of a problem for adult readers than for the children. And, for adults, part of the appeal of Rowling's books might be a reaction against trends in modern literature. "I have noticed an increase in people's interest in stories and story-telling," says Dr Todd. "We have had the post-modernist era, and challenging the way the novel is written, and now we are getting back to the good old story."

But while the strength of the story is important, in the end Rowling's books are much more than just a formula. Many of the parts might be familiar to readers of children's literature, but the author adds her own special blend which elevates them into something special.

"I read them all as soon as they came out," says Dr Todd. "I think the surprise element and the amazing imagination, are the main things. And, as far as educational psychologists are concerned, the books have done an amazing thing in encouraging children to read."

And while, in darkened theatres across the country, children will be staring wide-eyed in wonder as the flickerings of their imagination take shape on the huge screen in front of them, more than a few adults will be sitting among them, being transported back to their own childhood. And one of them will be a lecturer from Newcastle University's Centre for Family Studies.

"Children can imagine themselves as Harry Potter - an ordinary boy who finds himself in extraordinary circumstances," says Dr Anderson. "I can't wait for the film to come out, because I'm going to go and see it. My kids are too young, but I don't care."

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