Delia's sales droop as TV tie-in books go off the boil

Her choice of ingredients has provoked stampedes at supermarkets, and even earned her an entry in the English dictionary. But five years after she single-handedly saved a struggling family firm by endorsing its omelette pans on her BBC2 show, Delia Smith's appeal appears to be going off the boil.

Sales figures for her latest recipe book have revealed it is falling far short of its best-selling predecessors, which reached the dizzy heights of one million within months.

While far from being a flop, How to Cook: Book Three has sold at least 100,000 fewer copies in the nine weeks since its release than the second volume managed in the same period two years ago. Delia is not the only "guaranteed draw" from the realms of television whose star appears to be fading. A year after Simon Schama's A History of Britain became a must-buy for anyone with more than a passing interest in their heritage, Volume II, The Wars of the British, has failed to match its success. BBC Books shifted a very respectable 70,000 copies of the coffee table tome – but its predecessor did 110,000.

Likewise, the follow-up to the hugely popular companion to BBC1's Walking with Dinosaurs: while that sold around 100,000 copies in its first two months, its sequel, Walking with Beasts, barely shifted half that number in the period.

And in the wake of disappointing ratings for the comeback series of Absolutely Fabulous, an accompanying programme guide sold so poorly that its publisher, Headline, has declined to release any sales figures.

Despite such successes as Billy Connolly's biography, a number of other TV celebrity volumes have done poor business. Witness Bruce Forsyth's recent memoirs, for which he reportedly received a £300,000 advance: out last autumn, it has yet to top the 30,000 mark.

Indeed, industry observers now believe the TV tie-in market has finally reached saturation point.The latest batch of authors can at least console themselves with one thought. None has suffered the ignominy of what, in industry terms, has become known as "doing an Anthea" – a reference to the former Blue Peter and Lottery presenter's autobiography, which shifted just 1,000 of its 75,000 print run.