She was the queen of the kitchen stove. But then along came the young cooks with their fancy new recipes, so she donned her oven gloves and turned up the heat...

Like Marilyn Monroe, that other well-built, iconic old boiler, the Aga has such a cult following that books about it seem to sell like hot cakes. The latest publications are scenting the autumn breeze with a too-good-to-miss carrot traybake and olive, orange and rosemary biscotti. The first recipe is from the long-reigning queen of the Aga scene, Mary Berry, whose New Aga Cookbook is out in paperback. The trendy biscotti are from Amy Willcock's Aga Baking, one of two books by this hot new name on the simmering plate. Her other, Amy Willcock's Aga Know-how, is a pocket-sized paean to the joys of range cooking.

While Willcock is more like the Nigella of Aga cookery, Mary Berry is an institution. Not that there's anything as undignified as an oven-gloves-off sales battle between the two of them. Judging by book sales among 100,000 Aga owners, too many cooks aren't yet spoiling it for each other. It's just that Willcock has brought to the cosy world of wet Labradors, hotpots, steaming Barbours and laundry airing on the plate rack (no offence, mum) a touch of transatlantic chutzpah and rockbroker belt glamour.

Willcock is 35, and describes herself as a "vivacious scrummy mummy". She admits on her website that "modesty is not my strong point". With her husband and John Illsley of the rock band Dire Straits, Willcock owns three hotels, including the George on the Isle of Wight, where she lives. Although she was born in Chicago, her English accent could bring a snarl to Renée Zellweger's lips.

Her first book, Aga Cooking, sold 50,000 copies in a year, and her publisher is expecting the next two to do the same within six months.

But this isn't a two-woman bake-off. Louise Walker, like Willcock and Berry, is an Aga demonstrator and author of recipes for the cult oven, invented 80 years ago by a blind Swedish scientist and Nobel laureate. Her books have quietly clocked up about 150,000 sales. They're about to be joined in Absolute Press's catalogue by three more officially approved books in the New Aga Cook series. These are written by the editor of the Aga website and magazine, Laura James. Unlike the new Willcock and Berry books, they carry the three-letter logo. Willcock says the logo is not as instantly recognisable as the kettle and hot-plate lids, sketches of which adorn her pocket-sized book of tips.

"Aga is a star in its own right," says Laura James. It prefers to associate itself with cool famous people such as Jodie Kidd, who is proud to own an Aga, if not known for eating much cooked in it. Jamie Oliver is another unpaid ambassador; Sharon Stone and Ulrika Jonsson are other celeb owners.

Aga believes its "urban living" ad campaign successfully shook off the fug of the farmhouse kitchen and attracted younger buyers. It is popular on the East Coast of America, and France's second Aga shop has just opened in Paris. "It's a lifestyle buy," says Willcock, offering up more free advertising.

At one of her demonstrations (and book signings and cookware promotions), wearing a pink cardy and pearls, Willcock is a fluent, impressive performer. "What you'll notice with my cookware," she boasts, "is that it slides in and out of the runners. I'm a cross between Billy Graham and Pavarotti, aren't I?" she jokes, waving the Bake-O-Glide like a hymn sheet. Put another way, Amy has more front than Harrods' windows. Even if her ministry is not officially sanctioned, she proselytises across the nation for the cast-iron cooker from the Colebrookdale foundry.

Yet, "Mary Berry is who one naturally associates with Aga," says Laura James, whose husband Tim's book Aga: The Story of a Kitchen Classic, sold out in its first edition last year. So don't for a minute imagine that Mary Berry is history. Her new book has sold 60,000 in hardback and 5,000 in paperback already. "I love Mary," Amy volunteers. "Mary is the queen, not me. I'm the heir apparent." Hmm.

"Hasn't food moved on in leaps and bounds?" asks Amy, directing us to her pumpkin tarte tatin with chickpea flour, rosemary, chilli and balsamic vinegar, and her roast beetroot pizza. Mary weighs in with Thai prawns with coriander and noodles, prawn and boursin samosas and an apricot couscous timbale.

The Aga has successfully updated its image for next month's Breast Cancer Awareness campaign: it is selling 50 special-edition stoves in bright pink. For anyone thinking of buying a pink Aga (for £7,625, of which £1,000 will go to breast-cancer charities), decide whether you're more of an Amy or a Mary (or Louise or Laura) type. And if you've got your own chef - one who prefers flashy stir-frying to homely baking - don't buy an Aga at all. It's not what they're designed for. Unless you just want one to look cool.