There are some things which have to be said, even if they make one desperately unpopular with a nation's children. Some of us - and I'm speaking in a whisper here - are glad that the seventh and final Harry Potter book has been finished. In fact, not to put too fine a point on it, we're indescribably, heel-clickingly overjoyed that J K Rowling has written "fin" for the last time.

The author herself, it seems, feels the same way, describing a simultaneous sense of "heartbreak and euphoria" in signing off a publishing and marketing phenomenon which gave children's books a much needed boost and made her one of the richest women in the world.

But are we allowed, politely, to heave one very big sigh of relief as well? Some of us are weary of the hegemony even more than the hype. Some of us - well, OK, quite a lot of us - have come to regard Harry the global brand as a total bore, as predictable as Coca-Cola, as stimulating as a Big Mac and as profitable as Nike. We will be happy never to hear the name mentioned again.

Certainly, it is possible to describe as cultural tyranny the way in which Harry has dominated popular taste for the past decade or so. An astonishing 325 million copies of the books have been sold around the world, which has little to do with the intrinsic merits of a jolly saga about a boy wizard battling evil, but everything to do with the power of the marketing industry, children who are both less literate and more overtly consumer-conscious than previous generations, and parents clutching at a liferaft in the sea of their busy lives. This is a thing peculiar to its time.

The Harry Potter books are, as entertainment, inoffensive. But they're not literature; they're middle-brow pot-boilers. I will not presume to go as far as the great Yale professor, Harold Bloom, author of The Western Canon, who said of J K Rowling's work: "The writing was dreadful; the book was terrible. As I read, I noticed that every time a character went for a walk, the author wrote instead that the character stretched his legs'. I began marking on the back of an envelope every time that phrase was repeated. I stopped only after I had marked the envelope several dozen times. I was incredulous. Rowling's mind is so governed by cliches and dead metaphors that she has no other style of writing."

But I'm with Bloom in his demolition of the well-rehearsed argument which says that at least children are reading something, and that Harry Potter will lead them on to a life of reading - and, by inference, erudition. Now the first part of this argument does have something going for it: no doubt some children who would otherwise have spent their lives playing Grand Theft Auto: Vice City on their games console have been rescued from zombiedom by the gripping tales of Voldemort and Hogwarts.

But the second part doesn't hold water. Harry Potter will not lead children on to Swallows and Amazons, the Just So Stories, Wind in the Willows or Alice through The Looking Glass. What it will do, as Professor Bloom declared, is train them to read Stephen King. (Not, one gathers, a writer he admires greatly.) Certainly, in my own experience, the craze for Harry Potter books was a peer group thing for children, not unrelated to wearing the right brand of trainers. They were bought as status symbols and then languished, a quarter read, for years under the bed. How many of those 325 million copies failed to change the trajectory of the modern TV-raised child who, tragically, does not read for pleasure and probably never will? More than a few, I suspect.

So that's the elitist argument against Rowling, if you like: that her work is part of a general dumbing down; that in a way the whole Potter phenomenon represents a missed opportunity to stretch children's imaginations and teach millions the use of supple, challenging, original writing.

It's all a little harsh. Rowling's books are not that bad and have brought pleasure to millions. I remember as a child exactly the same kind of literary snobbery attaching to Enid Blyton books: speaking personally, I was forbidden Noddy and Famous Five books on those very grounds, but made up for it later with wall-to-wall absorption of Mallory Towers, read illicitly under the bedcovers by torchlight. Some would say they can see the malign influence still.

Where I really quarrel with Harry Potter is not in the quality of the writing but in the marketing. This Harry - Harry the brand - really is a monster of the first order. Somewhere along the line the author waved bye bye to her creation and saw it become a global money-making colossus, one which exploited the thrill of the chase and the tribal yearning to be part of something. It wasn't a book; it was a badge of belonging; a cult, Warner Bros. And more than 70 million Google entries. "I've got mine. Have you got yours?"

Oh, we fell for it. We were sent to spend nights queuing in the cold on Sauchiehall Street, in order to be the first to purchase one of those doorstopper hardbacks for our employers. This is when I perceived another worrying phenomenon: the rise of the adult fan. Frequently, the grown-ups queueing for their copy weren't doing it for nieces or nephews, but for themselves. In some cases their lips were moving when they scanned the lines, in other cases they didn't even have that excuse.

Read children's opinions of the Potter phenomenon, and they are surprisingingly thoughtful. "It's the most well-written book since Roald Dahl, but I still think it's over-hyped"; "Most kids don't know who Harry Potter is and only follow the crowd"; "When the film comes out I want to see if it's as good as the book".

Far more infantilised are the adults who have latched on to Harry Potter. Last weekend my colleague, Damien Henderson, in an admirable and thorough testimonial to J K Rowling's undoubted achievements, explored the commercial phenomenon that is Harry. He received an e-mail from an adult female Potter fan in the States, telling him she felt an "emotional, intellectual and personal" connection with him because of what he had written. The books, she said, had made her reflect on her own childhood and she was "enriched and satisfied".

Now all this is very sweet; and one can only be pleased that she and millions of fans like her are happy, but one does have to question whether J K Rowling is now being hijacked into territories which she never intended to visit. In that sense it is interesting that both the author and the young actor, Daniel Radcliffe, who plays Harry in the (largely lamentable) films, have expressed sincere relief at the end of the saga. Is it too presumptious to suggest that everyone creative connected with Harry has been imprisoned for too long in an immense money-making machine; one which has came close to crushing the original joy of an adequate story? I don't think so.