In a career of only three years, JK Rowling has changed book publishing.

She has created a world in which novels - like new cars, grouse, beaujolais nouveau and Star Wars movies - are mass-purchased on the first day of availability and in which book reviews are phoned in at half-time like a sports report. Saturday's newspapers and airwaves contained the first literary notices in which critics freely admitted that they had not had time to finish the book.

Selling literature like this is a risk. The only previous novel released to even a percentage of this hysteria, Thomas Harris's Hannibal last summer, suffered from critics taking revenge on the publicity. But while no writer could ever justify this hype, my view - backed, more importantly, by assistant critics from the target market - is that JK Rowling may survive it.

With an estimated £14m annual income and a global first print run of 5m copies for this book, Rowling is in obvious senses a lucky writer, but the fourth Harry Potter brings her another piece of author's good fortune: timing.

While the newspapers report the failure of England's bid to stage the football World Cup, Harry Potter and the Goblet of Fire begins with great excitement in the wizard homes of Britain over the staging in this country of the World Cup of Quidditch, Rowling's ingenious invented game.

It is such a happy coincidence that you read on half-expecting Harry to be arrested in Leicester Square after taking too many magic potions. But you should never make jokes about the commercial sorcery of Rowling: later in the story, a politician is indeed embarrassed by the actions of his teenage son.

Although the closeness to the Fifa announcement is an accident, the book feels thematically shaped to fit the summer of Euro 2000 and the Sydney Olympics. After attending a Quidditch World Cup final marred by incidents of hooliganism aimed at "muggles" (non-wizards) - a detail typical of the adult satire which makes her novels so parent-friendly - Harry's new term at his sorcery school includes an international Triwizard Tournament, a kind of magic Olympics.

In all the website speculation about what the book might contain, no one had predicted that Rowling would offer the most sporty popular fiction since the novels of Dick Francis. Those plot developments which had been floated - love interest for Harry and a climactic death - are present, though far less dramatically than anticipated. Romance is restricted to some minor blushy brushing and, with the killing, Rowling does not take the risk of thinning out the central cast list, using the old authorial trick of fattening up a character purely for the purpose of sacrifice.

Images of death and violence, however, do haunt the story, and it is here that the rising idea that the Potter books are some sort of universal literature suitable for infant school or pension queue needs to be questioned. My five-year-old assistant critic had a troubled Saturday night after hearing the first hundred pages.

Whereas Enid Blyton's characters passed decades without celebrating a birthday, part of Rowling's concept is that Harry is 12 months older each time she publishes. In this fourth novel, there are signs that this trick is taking her away from younger fans. For example, Harry and friends use the expletive "git", for which some parents and infant teachers may not feel ready.

As for the view that the Potter novels pass as adult books, any dedicated grown-up reader would need to be frightened of what real life and real writing are like. Rowling's prose is correct, but there is never a surprising sentence.

Purely as a children's author, though, the fourth Potter confirms her as an original who takes her craft seriously. Most publishers will privately tell you that huge success is often ruinous to a writer's talents: the books they write poor are usually better than the ones they write rich. But Harry Potter and the Goblet of Fire suggests that Rowling still wants to write big books as well as big cheques.

• Harry Potter and the Goblet of Fire by JK Rowling, Bloomsbury, £14.99 hardback