THERE IS A STORY ABOUT THE time when J. K. Rowling was having lunch at her publishers, Bloomsbury. They were urging her to keep writing the Harry Potter novels, and not to stop in his seventh and final year at Hogwarts.

“I know,” said one publicist brightly. “How about Harry and his friends have a gap year?”

Rowling drawled: “What makes you think he lives that long?”

A horrified silence. Then she added, impeturbably: “Just joking.”

Who, oh who, will replace Harry after the publication of the final book this month, Harry Potter and the Deathly Hallows? If children feel inconsolable, the publishing and film industry are far more agitated. Such is the desperation to get in on a $7 billion global business that when J. K. Rowling's original editor, Barry Cunningham, announced last month that he had found “the new Harry Potter” in a debut novel called Tunnels there was a flurry of publicity and many Hollywood studios instructed producers to bid for the rights without having read a word of it.

A number of them read my reviews in The Times and asked my opinion, so I was able to tell them not to bother. There is far, far better stuff out there. The problem is that, good as it is, it may not feed the appetite that Harry Potter stimulated.

Quite what has made the series unique needs to be disentangled from the story of J. K. Rowling herself. Its extraordinary success is down to many factors: the author’s touching personal story, the strict embargo that made publication increasingly newsworthy, the appealing cast of fresh young actors and grand old thesps in each film, and the wizardry of computer-generated imagery that has made magic look real. Yet the more interesting aspect is both demo-graphic and literary.

The Harry Potter books arrived at a particular point in publishing history. Falling birthrates and rising incomes among the growing middle classes have made childhood more materially indulged, more fretted-over and more sedentary than at any time. As his publisher David Fickling observes, the internet has fed Harry’s fan-base, so that “part of the enjoyment is being able to talk about it with everybody else. It’s a culture magnified by the internet.”

Yet it was Philip Pullman who reminded publishers of the unique virtues of children’s fiction. A year before the first Harry Potter novel, accepting the Carnegie Medal for Northern Lights, he made an important speech about storytelling. Bored by decades of literary fiction in which novels were supposed to be read purely for their style, adults were primed to discover a new source of entertainment and genuine intellectual stimulus in children’s fiction, which had never ceased to tell great stories and illustrate important questions about the human condition. J. K. Rowling was in the right place at the right time; she caught a wave of nostalgia, curiosity, boredom and fashion that may never be repeated. Nobody expected it to happen and, if it does occur again, it is likely to succeed in the same way as did Rowling, through word of mouth rather than through hype and marketing.

The author’s own Cinderella story has almost eclipsed what makes Harry Potter so special. Being young, poor, pretty and a single mother captured the public imagination more than the fact that, as a former teacher, she was always more likely to know what would keep a child’s attention. My guess is that Rowling will prove unique. Nobody will fill her shoes, simply because no author can ever fill another’s place. They can only grow into their own – something that too many publishers and booksellers today, with the obsession about marketing, prizes and TV shows, appear to have forgotten. Yet talent follows money, and her success has at least ensured that a new generation of outstanding storytellers will join her for at least the next decade.

After consulting editors, publishers and booksellers Books has compiled the run-down of ones to watch opposite – they may not fill Harry’s shoes, but they’re treading on his heels.

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