A Week in Books: Is the golden age of children's books over?

It ought to count as an iron law of modern culture that, whenever Madonna starts to show an interest in an art form, its days are numbered. If so, the children's book world should watch out. The tarnished icon whose last literary effort (Sex in 1992) managed to lower the tone of bondage porn will publish the first of her five children's stories with Puffin in September: The English Roses. Her US distributor praises La Ciccone's "lifelong passion for and deep familiarity with" children's literature.

News to many, I imagine. What we have observed is Madonna's lifelong passion for artistic fashions – from metallic undergarments to Mockney gangster flicks – which are just about to drop off a cliff. Her own interventions, of course, might have something to do with that collapse.

Officially, the boom in young people's fiction that began with the Harry Potter starburst in 1997 still thunders on. This week, around 1,400 companies from across the world have been seeking to buy or sell the next junior sensations at the annual Bologna Children's Book Fair, which ends today. Much-trumpeted six-figure signings proliferate: Louisa Young and her daughter Isabel, with Puffin's Lionboy trilogy; David Lee Stone with his Illmoor Chronicles for Hodder; or Katherine Langrish's Viking swashbuckler – Troll Fell – destined for HarperCollins. By and large, the amply funded newcomers of the post-Potter generation have paid back their patrons, although not as swiftly as publishers might hope. (Eoin Colfer, creator of Artemis Fowl, currently ranks as the 14th bestselling children's author in a chart topped by Rowling, Wilson and Pullman.)

Yet, unofficially, this "golden age" already feels stale, sour and leaden. The publication of Harry Potter and the Order of the Phoenix on 21 June will probably pay the year's bills for thousands in the trade. How many of them positively look forward to it? Time was when children's publishing offered a haven to enthusiasm, earnestness and (not least) eccentricity. Too much of a haven, maybe: but now, every scatty and spontaneous impulse has fled as the sector joins the usual winner-takes-all stampede.

The cult of the children's superstar means less attention, and lower advances, for everybody else – however talented. Corporate values prevail. Meanwhile, the overall size of the children's market (here's a classroom secret) remains static. Harry Potter and Artemis Fowl may well be winning what the mathematicians call a zero-sum game.

One way out of the corporate echo chamber would be for authors to restore direct hype-free links with their young readers. An enterprising guerrilla group of children's writers, the Scattered Authors' Society, now aims to do that through visits to schools and shop-based campaigns. It harbours some renowned names, such as Susan Price, Celia Rees and Adele Geras. You can find out more about the undercover activities of this SAS via wordpool.co.uk.

Good children's authors still delight in choosing for their heroes and heroines plucky outsiders whose wits and guts help them to overcome the bullies, creeps and conformists. But such bracing tales of triumph against adversity have less and less to do with the business that promotes them. In the world of children's writing, Prince Charming still marries Cinderella. In the world of children's publishing, the opposite now occurs. The Prince doesn't merely marry an Ugly Sister. The pair then proceed to set up Slipper Solutions Inc and build a Warner-franchised entertainment complex over the razed ruins of Baron Hardup's castle.