Something needs to be done about this mania for stage versions of 19th-century classic novels, and soon. Censorship is an ugly word; but really, how would our civil liberties be offended by a modest little piece of legislation banning (say) adaptations of any novel more than 100 years old and 100,000 words long?

Which is not to say that good things haven't come out of the adaptation craze - Shared Experience's Mill on the Floss and Mike Alfreds's version of Sheridan Le Fanu's shocker Uncle Silas both demonstrated beyond argument that, for all their wordiness and complexity, some Victorian novels can become exciting, moving theatre.

Some, but not all. In prospect, a version of Jude the Obscure, Hardy's masterpiece, by Mike Alfreds and his new company, Method and Madness, sounded wonderful; with hindsight, you can see that Alfreds and his cast of four were biting off more than was sensible. The novel follows, often in excruciating detail, the career of Jude Fawley, a stonemason with scholarly leanings whose ambitions are thwarted by his lowly station in life, and by a foolish early marriage to the unsuitable Arabella.When he does find happiness, with his intellectual cousin Sue, it is threatened by the unconventionality of their relationship - both divorced, and unwilling to remarry, they are outcast from respectable society.

There is an awful lot of story to fit in, including some highly charged dramatic incidents - there's little in English literature as sheerly appalling as the suicide of Jude's son by Arabella, who hangs himself and his half- brother and sister, leaving a note explaining: "Done because we are too menny." In this version, the story moves along at a cracking pace; but it's the pace that kills.

It kills the impact of individual episodes, such as Jude and Arabella's disastrous foray into pigsticking: in the book, the squealing, bloody pig seems to take forever dying; here, it's a quick bit of fun with a pink latex piggy-wig and a squirt of red liquid, and the contrast between Jude's well-meant fumbling and Arabella's heartless resolution is fatally blurred.

It kills the sweep of the narrative. Time and again, emotions blow up which seem to have no proportional cause in events; when Jude and Arabella come to blows over his books, there's been hardly any time to appreciate the tension in their marriage, and his devotion to books has been asserted rather than shown. In the second half, there's little sense of the slow erosion of Jude's hopes, just a catalogue of incidents - so that the collapse of his health and his final illness seem like afterthoughts rather than an integral part of his tragedy.

And it kills the performances - Geraldine Alexander's nervy, mannered Sue seems exactly right to begin with; but, over three hours, her acting seems to reduce to nothing but mannerism; there's no room for her to develop the part. Martin Marquez's Jude isn't so monochromatic, but it still feels more like a sketch of the character than a fully fledged performance.

The sense that events are just flitting by, whoosh, is emphasised by the scale of the production. With only four actors, the focus is inevitably narrowed to the personal relations of Jude, Sue, Arabella and Sue's husband, Phillotson. What we miss is the social context - which is everything. With Uncle Silas, this kind of simplification didn't matter; it might even have done Le Fanu a few favours. But Uncle Silas is melodrama, in which the fewer distractions you have from the bare essentials of plot and febrile emotion, the better. Here, the frustration of Jude's scholarly ambitions, the collapse of his and Sue's attempt to lead a rational, loving life, are social tragedies, proofs of how institutionalised marriage and institutionalised learning stifle the impulses of the heart and the mind.

You also lose any sense of locale. Paul Dart's set and lighting work ingeniously - a few low wooden boxes and some high wooden window-frames, set on wheels, are shunted swiftly and gracefully around the stage; in conjunction with lighting changes, they create an impressive variety of spaces, from church to pub to bedroom to Oxford college. But the very fluidity of the set works against Hardy's sense of place, and the feeling that the buildings of Christminster (Hardy's Oxford) embody the crushing weight of convention.

I hope this doesn't sound like the dreary whinge of somebody who's read the book and isn't going to allow the stage version to interfere with his idea of it. The sad truth is that a very fine director and a good cast have exerted their obvious intelligence to turn a great novel into a dull evening at the theatre. It's a near miss; but you know what a miss is as good as.

More disappointment at the Mermaid, where Steven Berkoff's production of Coriolanus has arrived, with the great man himself in the title role. I hardly like to speculate on the psychological factors underlying his long-running affair with the play - this production has been running on and off for eight years now. What on earth can Berkoff find to attract him in the character of a brilliant leader unfairly driven out by his own people because of the fear and envy he arouses in lesser men? Surely he can't feel that this story has any bearing on his own place within British theatre.

Well, of course he can. And at the risk of fuelling his paranoia, this Coriolanus comes pretty high on my personal list of all-time theatrical stinkers. The problem isn't that Berkoff's stylised theatre doesn't work with Shakespeare; there are moments here where it works brilliantly (when, for instance, the exiled Coriolanus presents himself at the camp of the Volscians: the Volscian army immediately explodes into a brilliant parody of a Hollywood SWAT team). But a lot of it is plain silly - the martial- arts battle scenes, with the ensemble furiously shadow-boxing and kicking at the air, lack any aggression or menace.

The main hitch, though, is Berkoff himself. This Coriolanus is so absurdly actorish - putting on silly voices, telling jokes, prancing and posturing and waving his hands in the air to make his point. Showing off is part of the character, certainly, but so is utter rigidity: a Protean Coriolanus, one who's more alive to the subtleties of rhetoric than his opponents, just doesn't make sense. In the Guardian last week, Michael Billington said that Coriolanus made more sense when he went and sat at the back of the theatre, and that sounds plausible. Go and see it, by all means, but from a safe distance.

We can at least end on an upbeat: Patrick Garland's jaunty production of The Tempest at the Open Air Theatre in Regent's Park is clunking, but clunking is what works here; and anybody who dares to put Christopher Biggins on stage in long-johns has a sense of the grotesque that makes up for an awful lot.

Theatre details: Going Out, page 14. Robert Butler returns next week.