Ian Kiaer, Alison Jacques Gallery, London

Of all the devils to plague a young artist, the most sulphurous is success. You're 26; you find your voice; you spend 10 years doing what you do: then what? How do you move on?

If you're Ian Kiaer, the answer is very, very gently. Kiaer is 36 but found his voice - precise, clever and quiet - a decade ago. In a world of Big Boy Art - jewelled skulls, epic machines, Matthew Barney - he chose to make work that was small. I don't mean in terms of size (it's hard to know where Kiaer's art starts and stops, though it often takes up a whole room), but of its vocabulary and grammar. Kiaer's palette runs from washed-out blue to watery lemon, his materials from the cheap and disposable to the pre-thrown-away. His handling of these is likewise invisibly slight. Find a piece of Styrofoam on a gallery floor and you're probably looking at a Kiaer.

There's a fragment like this in the back room of his London show, a work (and a setting) that ties the artist to his past. Above it on the wall is a sheet of paper with a splat of yellow on it, next to this a white paper bag of the kind used for hamburgers; in front of these, apparently for the visitor's use, is a stool of silvered cellophane and card. The thought of sitting on this, the disaster that would follow, makes you wince. Kiaer reminds us of our bodily weight and, by extension, of the heaviness of our gaze. In its delicate way, his work demands to be looked at delicately.

It would be easy to use the word<U>Minimalist</U>of all this, although it would also be wrong. Echoes of Robert Ryman's white-on-white bricolage are distant and misleading. Kiaer is a formalist, his tentative constructions setting up a flutter of mind and eye from colour to pale colour, texture to texture, association to association. That refinement is what his work is about, but that isn't all.

As it happens, this new show is based on time Kiaer spent in the market area of Seoul in South Korea. At the sharp edge of globalisation, the Ulchiro district is in a constant flux of self-destruction and reinvention. Impermanence and detritus are what capitalism is about, the unending pressure of novelty. And you feel that, somewhere in this unpromising mix - the Styrofoam packaging, the paper bags - Kiaer has found a parallel with his own life as an artist, the need to bring new things to market.

And so the things he brings are those of the market, gently manipulated in the manner of Kiaer. (His name, as you'd hope, is pronounced "care".) Some of these feel like the artist we're used to, the one in Tate Britain's Art Now series three years ago. There is a pair of small canvases low on the wall - one coarse-woven and flesh pink, the other smooth, white and grubby - and a piece of pink expanded foam, what may or may not be a city built on it in folded card. This last is printed with Korean text. You have the curious sense of hearing a language that sounds intricate and beguiling, but whose meaning is entirely hidden from you.

So far, so Kiaer, although two other pieces in the show are less expected. One is an inflated cube of white plastic sheeting that seems mildly amiable, like a cartoon ghost; the other is the wilting steel frame of a billboard, its message its own message-less fragility. It's an intensely clever piece this, the carrier of signs reduced to a sign, a frail advertisement for frailness. You might read it as political, although really it is a depiction of Kiaer and his place in the world just now. Brilliant is the only word. It is probably beyond my powers of persuasion to convince you that a small gallery full of nearly nothing adds up to the best show in London, but it does. See it.

Alison Jacques Gallery, London W1 (020 7631 4720) to 22 December

Further reading 'Minimalism' edited by James Meyer, Phaidon 24.99