In his programme notes, director Samuel Miller describes Neil LaBute's 2001 play as a "modern classic" that "found its way into the cultural zeitgeist". This is as a generous verdict. The zeitgeistiness may be fair – though it's difficult not to feel it's a touch retrospective; a consequence of the subsequent career success of the original production's leads (Rachel Weisz and Paul Rudd) – and that, unusually for a stage play, it was immediately adapted for the film screen with the original cast after it finished touring (though on a small budget it still made a loss). The modernity is less assured. The opening scene features a pair of American college students neither of whom carry phones or pens but who are happy enough to improvise (unconvincingly) an exchange of their contact details with spray-paint, an approach which seems more eighties than noughties. As for its status as a classic... well, I would say the jury's out. Yet even if Miller's judgement of the play is a little overwrought, his direction of it is intelligent and well judged. Allied to an excellent cast and some innovative set design the production seems more consistent than the play itself, which doesn't always deliver as much as it seems to promise.

The Shape of Things is intended to work on several levels. At first glance it looks like a love story that might even pass as a fluffy romantic comedy; at the next it seems to be a slightly acidulous take on relationships as two couples clash; at a third level it seems guided by less than subtle religious metaphor (the lead characters are called Adam and Evelyn; they kick off proceedings by critiquing a statue of God in a gallery). At a further remove, the play wants to be a meditation on the nature of art itself. In the film version an aphorism appears on the wall of an art gallery: "Moralists have no place in an art gallery". A striking judgement the play, for the most part, seems to want to endorse.

That the artistic debate matters more here than the religious is signaled in the re-imagining the neoclassical statue of God of earlier versions, as a large piece of conceptual art in the form of an amorphous sky-blue blob (it doesn't look like anything; but it definitely doesn't look like anything anyone would ever call God). As the play continues the blob disentangles into smaller items, from coffee shop chairs to beds; though these themselves are rarely precise. It's a lovely metaphor not only for the changing behaviour and appearance of Adam as he falls (another LaBute pun) under Eve's spell  –  but it also makes for a neat parallel with the necessary interpretations and interpolations made by theatre audiences as they fill in the missing parts of the setting and story from the scenes presented (we know the bottom ledge of the blob isn't a bed but drape a sheet over it and strip the actors to their jim-jams and we see one).

For all these bells and whistles however the play's enviable power is generated by a rattling plot which keeps up the suspense and twists without ever entirely losing credibility (perhaps because it never quite has it to begin with). This is particularly the case in the final surprising act which will gazzump most newcomers.

Though much the same age as the original cast, the actors still feel disconcertingly old for the parts they're playing. Even so Sean McConaghy as Adam is a wonderfully sympathetic lead, shrinking into the age of awkwardness as though he never left it, while Anna Bamberger's slightly hysterical Eve (a very unselfish performance) is an excellent foil. Her mania seems closer to the spirit of LaBute's text than the softened ages Weisz used in the film version. Harrie Hayes and Sean Browne in the supporting roles of Jenny and Philip, also mix tenderness with gaucheness. With apposite brashness, when alpha male Philip's masculinity seems under threat he reappears in his next scene juggling an American football.

Even so in trying to highlight the play's interest in Art with a capital A – and equally in neatly dumping the schematic religiosity – the production inadvertently reveals the play's essential glibness. The Shape of Things isn't really about the morality of art at all (there's no sense for example, that LaBute has wrestled with Wittgenstein's assertion that "ethics and aesthetics are one"). Instead it's concerned with power and LaBute's narrow but compelling view of agonistic human relationships.

In a revealing interview, when challenged on whether he believed in the aphorism that moralists didn't belong in galleries, he slipped quickly from art to violence.

"I think moralists have a place in an art gallery, I think everybody has a place in an art gallery, they just should keep their mouths shut. They're free to walk around as long as they pay the price, I just don't think they should be dictating policy. I'm big on the argument the film proposes about subjectivity about art itself. This glass of water can be art because you made it, or it can be a glass of water to me and I can think you're a loon for calling it art, and we could both be right. So I'm big on 'I'm okay, you're okay' but if pushed, it turns quickly into 'I'm okay, you're a piece of shit'.

Because ultimately... I'm happy to come out even, but if forced, I want to come out on top."

Beneath whatever people are outwardly talking about they're fighting to win, and they're fighting to win all the way down.

The Shape of Things, at Arcola Theatre

It's quite possible to find LaBute's play unpleasant, insincere and glib. Yet as this solid revival shows it remains difficult to resist. At the Arcola Theatre.

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