IF you know the name without knowing the work (Hamlet, Oedipus, Winnie the Pooh, Paddington Bear, Alice, William, Noddy, Anne of Green Gables, and so on) you are in the presence of a bona fide hero: a free-standing character who is not simply contained in a work of the imagination but ranges across the cultural landscape. The latest recruit to this pantheon is Harry Potter, the brainchild of JK Rowling.

Put aside any Aristotelian ideas of great men brought low or fatal flaws.

Harry is a child. He is also a wizard, and the child of wizards, but at the beginning of the saga he is living with Muggles (non-wizards), and horrible Muggles at that. The first book, Harry Potter and the Philosopher's Stone, sees him transported to Hogwarts, a boarding establishment for apprentice sorcerers, where the curriculum takes in everything the young necromancer could desire and where a glorious game called Quidditch is played: a sort of football on broomsticks, with regulations which make the intricacies of the offside rule appear straightforward in comparison.

Every hero needs a sidekick - think of Don Quixote - and Harry has two. Between them, Harry and his friends, Ron and Hermione, provide all the qualities needed in a threesome dedicated to (basically) the on-going fight of good against evil. It's all written with great brio; it's funny and scary, though not too scary, and it has captured the imagination of everyone you speak to, regardless of age.

Fathers, perhaps lured by the rather old-fashioned look of the cover art, read it to their children and took to sneaking it off to work with them. Bloomsbury obliged by bringing out an edition which adults could read in public without immediately drawing attention to the blush-inducing fact that they were immersed in a children's book.

Volume Two, Harry Potter and the Chamber of Secrets, was as popular as the first, and the third, which is due for publication on 8 July, is being super-hyped by those critics who have been allowed a glimpse at the proofs, those same critics first having to sign an agreement swearing not to divulge the contents before publication, as if that would make the slightest bit of difference to the rapturous reception the book is sure to receive.

What is it, then, that has turned the Harry Potter stories from popular to phenomenal? What does a writer have to do to create this astonishing creature, the true hero? The short answer is that if we knew, then we'd all be pumping out Potter classics while conferring full-time with our accountants and assorted Hollywood producers. That, then, is the first thing that needs to be said: you cannot simply decide to do it any more than you can make your mind up to write a best-seller. Heroes become heroes for a variety of reasons.

Sometimes (Hamlet, Oedipus) the work is so great, so universal, that succeeding generations and all sorts of cultures find something in it.

Children's heroes, both male and female, fall into two separate categories. There are those who are observers (Anne of Green Gables, or Alice, or Jim in Treasure Island), and the pleasure for the reader of any age is to borrow that person's eyes and see the world as they do. They speak for the young readers, and react for them. The other kind of hero is the one we would like to be.

In Richmal Compton's stories, for example, William allows us to be as naughty as we like in our imaginations without needing to fear punishment, or even disapproval.

We can be anarchists by proxy.

When we open a book about Harry Potter, we can see an enchanted world through both Harry's eyes and, by proxy, the eyes of wizards', allowing us to re -arrange anything with a wave of our magic wand.

Harry is like us: he is weak, ordinary and has all the fears which most of us have. He is, at least at the beginning of the first book, friendless and unloved: alone against everyone. Most children feel that this is what they are, at least some of the time, and it's wonderful to read about how others deal with it. As well as being ordinary, though, Harry is clever, loyal and, best of all, brave, and these are all qualities which children would like to attach to themselves. Also, he is quite clever without being a swot. It's Hermione who is the real brains of the trio.

Another interesting thing about the books is that they fall into a tradition of school stories, and more especially school stories in a series.

These have always been popular.

Think of Billy Bunter (another hero); think of the Chalet School series; think of Malory Towers; think of Angela Brazil. The series element is important. If you like something, you are comforted by knowing there will be more where that came from.

Continuity is one of the things which admirers of soap operas like, and school stories are simply a junior form of soap.

The advent of the comprehensive school meant that writers largely stopped writing about rich kids in boarding-school. However, Grange Hill was very popular on TV and shared with other soaps a recognisable setting and a fixed cast of familiar types: the bully, the swot, the eccentric, the coward, the beauty, and so on. It helps if the setting is closed. It works wonders for the narrative if your characters are trapped in some way and can neither get out to the wider world nor have the wider world come and interfere in this microcosm. As a result, jails, hospitals and schools have an advantage, and even stories set in supposedly real places are generally confined to one street or square or grand house.

Hogwarts Academy is the perfect setting: a Gothic creation somewhere between Gormenghast and every boarding school there ever was, including the one I went to for eight years. Teachers, too, whether human or magical, are too good a collection of characters for a writer to ignore. "You never forget a good teacher," the slogan goes, and novelists never do. Their pages are stuffed with versions of the people who taught them when they were young. There are, after all, very few adults who are more closely observed by the children with whom they come into contact.

Harry Potter's universe is a comfortingly closed world, then, and he and his friends go through all sorts of exciting (and fantastical) adventures on our behalf.

Add to this an absolutely brilliant publishing campaign from Bloomsbury, which knew, for example, that Ms Rowling had to call herself JK and not Joanna, because boys would not buy books with a female author's name on the cover. It also realised that it had boy-friendly books on its hands, and made a point of saying so. It was quick to respond to the first good reviews in the specialist papers with advertising, lots of interviews, and shrewd choices of where, and how, Ms Rowling should be seen.

It is true that the books are good books, and it's true that the audience for them is wider than many others which immediately rule out half their readership because they're perceived as "girly." It is also true that in order to create a hero, it helps to have a finely honed machine which can swing into full hype-mode when required. Success breeds more success. Once you tell everyone that the movie has been sold for a seven-figure sum, you bring in readers who are there out of curiosity, and so on. It's a snowball effect.

There are going to be five more Harry Potter books. We are ready to follow him into adolescence. All sorts of plot strands will only come to a conclusion in a few years' time.

This means that when you embark on a saga like this you commit yourself, and that's part of the fun. You're one of the ones in the know: a Harry Potter fan. You can swap words and catchphrases which mere mortals won't recognise. You can make allusions that go over the heads of the ignorant. It happened in the USA with the Tolkien books when they became a cult with students. You belong to a club.

So what does having a hero such as Harry bestriding the world like a colossus do for other children's books? A children's writer friend of mine (who shall remain nameless) was saying ruefully the other day that "every single prize awarded by children will go to a Harry Potter book for the foreseeable future".

This is quite true. You have also to bear in mind that children keep on growing and new readers spring up all the time, and move on to Harry Potter and more Harry Potter. If this makes avid readers of them, in the way that the Enid Blyton books made readers of my generation, then they are to be applauded. The hope must be, however, that those who have immersed themselves in the saga will go on and on to other heroes and different sorts of books.

It's possible to imagine someone staying in the realms of magic forever, and moving seamlessly from Rowling to Pratchett and Peake. It's up to adults to dig deeper and direct children towards the rest of the fictional universe, which has many other completely different marvels in it.

Adele Geras has written more than 70 books for children of all ages. Her latest novel for teenagers is Silent Snow, Secret Snow (Puffin, GBP 4.99).

Copyright 1999 The Scotsman Publications Ltd.

Original page date 2 March 2007; last updated 2 March 2007.