It is a truth universally acknowledged that an author in want of a plot, turns to Austen.

I am, for the first time I can remember (and I've been reading for 32 of my 36 years), considering not completing a book. Normally I'm bloody-minded enough to battle my way through a bad book on the grounds that I've spent good money on it. Also, many bad books are culturally significant in some way (I'm thinking of Hornby and Parsons here).

I must confess, however, that P. D. James's Death Comes To Pemberley is on the verge of defeating me. It is quite the worst book I have read since How Green Was My Valley, about which I wrote my PhD thesis (and a forthcoming best-selling exposé, or 'journal article' as we call them in the trade), as a form of catharsis.

I'm a bit of a Jane Austen obsessive. Her interests are not my interests, her world and beliefs are not my beliefs, but the sheer quality of the writing renders that irrelevant. I'm also interested in what subsequent cultures have done with Austen's work - often made it more dull, sometimes highlighted the troubling or radical impulses which are detected, and at the moment, turned to satirical responses. Clueless is one of my favourite films: a whip-smart adaptation of Emma. I own multiple copies of the novels because I'm interested in the different ways cover design and blurbs are used to reposition Austen, such as for the 'chick-lit' market. I also own Pride and Prejudice and Zombies, Dawn of the Dreadfuls, Sense and Sensibility and Sea Monsters, Pride and Promiscuity: the Lost Sex Scenes of Jane Austen and Pride and Prejudice: Hidden Lusts.

All of these are superior to P. D. James's Death Comes To Pemberley, an attempt at a country-house murder sequel to Pride and Prejudice. Why James thought that an Austen murder-mystery was required is in itself a mystery: Jane wrote one of those herself, called Northanger Abbey, in which she expressed very clearly and hilariously her distaste for cheap thrills and sensationalism.

The most obvious fault is the author's determination to shoehorn in her own very reactionary politics. James is - in addition to being a best-selling crime author (I recommend Children of Men), a Conservative peer in the House of Lords. In this novel, she repeatedly goes out of her way to demonstrate that servants love their employers and depend on them for support and sustenance. They're grateful, obedient, unobtrusive, grovelling and wholly without character. They are - in the dread phrase of the nanny-employing classes - 'part of the family', albeit a part of the family that doesn't get to speak or go above stairs.

There's also a very weird passage in which two magistrates (one's kind, one's strict but they both have the interests of justice at heart - like a bad ITV drama) discuss the legal system. James spends several paragraphs explaining why courts of appeal are a bad idea. Despite the whole depressing history of British justice going wrong (for example: the Birmingham Six), James seems to think nobody has ever been wrongly convicted and therefore appeal courts and judges in general should be abolished in favour of a single jury trial before the prison doors clang shut. Why this should be in the novel at all is beyond me: it's far worse than the socialist propaganda novels so roundly mocked by the literary elite.

James also appears to have a cloth ear for dialogue and language. Characters are 'depressed', which strikes me as a very twentieth-century use: the term existed in Austen's day, but not quite in the same sense. Characters repeatedly refer to familiar people by their full titles, such as Sir Selwyn Hardcastle (he's one of the magistrates, and in case you're so dumb that you don't notice, the narrator steps in to make the point that his name suits his 'firm but fair' crusty administration of justice). I don't know whether PD expects her own friends to address her as Baroness Phyllis Dorothy James of Holland Park at all times, but she should surely know that the knight would be referred to as 'Sir Selwyn' by most people. It all gives one the impression that the novel's been written by an American tourist.

However, the worst element of the novel is the constant fecking exposition. Incapable of a prose style other than breathless yet plodding romantic-realism - as though Austen was typing while wearing boxing gloves rather than delicately painting on 'this little bit (two inches wide) of ivory' - James sticks the most embarrassing passages of expositionary dialogue on every other page, interspersed with tedious, patronising narrative commentary which serves only to prove that a) she's no Jane Austen and b) she thinks her readers are thick as pigshit.

You can't turn a page without a character saying something like 'Remind me again where you met. It was in London at your lawyer's office was it not?' 'Why yes, it was, but I'll tell you all over again because there might be readers out there who don't know, and that would be totally bogus dude. I mean, Sir'. This stuff is all over the place. I recommend How To Write Bad Exposition to the Baroness, because her novel is every bit as bad as this example:

John: I've been so upset since Margaret died.
Jane: Margaret? Your wife?

I'm half way through. I'm firmly convinced that P. D. James neither reads nor understands good fiction. There's no structure, no confidence in the subtle power of words, and no sense that she's addressing an intelligent reader capable of inference. Ambiguity and complexity have no place in this novel. A literary and political travesty which displays contempt both for Austen and for us.

If you're going to write a pastiche of a famous, well-loved novel, you need more than presumption. You've got to have a perfect ear for language - James assumes that 19th-century dialogue is achieved simply by removing contractions and making hilarious comments such as 'this is the nineteenth-century, after all' and you've got to have a bit of respect. You might think that Pride and Prejudice and Zombies, Clueless and Pride and Prejudice: Hidden Lusts would be cheap, cynical cash-ins and James's novel be a serious homage by someone with a real affinity with Austen's world. You'd be wrong. The parodies work beautifully because their authors understand language and dialogue, they know how to structure a work of art, and they actually love and respect Jane Austen. This gives them the confidence to take dreadful liberties with their heroine's work and succeed. They know what they're doing, so they can relax, be jolly, have a romp. By contrast, Death Comes To Pemberley is a smash-and-grab raid. James steals familiar characters and settings and shoehorns in a bad plot, clunking dialogue and inappropriate political homilies without any of the respect shown by the parodists for the same source material. She thinks this is her world - though the various anachronisms make it very clear that it isn't - and is too snobbish to have any fun. Jane Austen she ain't.

Less Death Comes to Pemberley, more Death Comes To Dialogue.