'Jane Austen (can we really believe that name? I imagine some corpulent copywriter with a tax-bill to pay) makes a very poor fist of Mrs Bennett'

I've been reading Pride and Prejudice recently, a novelisation of Andrew Davies's classic television series of the same name. The paperback is adorned with a full colour photograph of Colin Firth as Mr Darcy and Jennifer Ehle as Lizzie, so I think there's little doubt that it is a shameless attempt to cash in on the success of the original, now drawing over 9m viewers every week. And while I don't want to sound puritanical about it, I have to say I'm a little disappointed with the liberties that have been taken with Mr Davies's creation.

There are those, of course, who defend such translations of a work of art into another medium. They believe that such processes bring the work to a new audience. And though they concede that most purchasers of the book will simply wolf it down unthinkingly and pass on, they argue that a few might be introduced to the rarefied intellectual pleasures of the classic serial. If a coarsening of the original intention takes place, then that is a reasonable price to pay.

There is something to be said for this argument, it's true, but I'm not convinced it can survive the indignities of the actual text. As you turn the pages it becomes clear that there is no thought of fidelity in the mind of the hack who has produced this catchpenny spin-off. On page after page, glaring errors and omissions can be found, suggesting that the writer has no feel for the merits of Mr Davies's work, no respect for the genre conventions of the television serial.

Take the characterisation first of all: Jane Austen (can we really believe that name? I imagine some corpulent copy-writer with a tax-bill to pay) makes a very poor fist of Mrs Bennett. Instead of Davies's immortal creation - a character that bears comparison to some great television predecessors - Bet Lynch in Coronation Street, Hyacinth Bucket in Keeping Up Appearances - we are offered a strangely depleted version. Not unamusing, to be fair but you can't quite shake off the feeling that this is a woman you might meet in the street, that she might live next door to you. Austen, I'm afraid, has no real flair for grotesque caricature.

At least with Mrs Bennett you feel she has tried. But Darcy is subject to truly perverse alterations. He is several times described as smiling in the book when everyone knows that Darcy's unchanging facial expression is that of a man who has just been obliged to shoot his own dog - that fixed scowl is what gives the early parts of the story its distinctive flavour. Austen's Darcy lacks this striking clarity; if you were being kind you might describe her account of him as ambiguous. Vague would be closer to the truth.

There are numerous other instances of small betrayals. The socio-political context - so deftly sketched in by Davies with vignettes of the coachmen drunkenly aping their "betters" outside the assembly rooms - is completely missing in the Austen version, as if she simply couldn't be bothered to address the question of the rural poor in squirarchical economies. Speeches are lifted from one scene and placed elsewhere: Lizzie's teasing about Mr Wickham's defection, for example, ("Handsome men must have something to live on, as well as the plain") is no longer made to his face, as it is on screen, but in an aside to an aunt - which makes Lizzie appear almost decorous, rather than the feisty coquette we know and love.

Worst of all, and most mysteriously, there is hardly a word about the clothes, the interiors, the meals. Where Davies gives you a cornucopia of period detail, rich in colour and texture, Austen supplies only the most cursory descriptions. Such things are harder in prose, it's true, but Austen's indolence in this respect is unforgiveable. All she seems to care about is what people do and what they feel, not what they look like and what they wear.