Presidency, Sprüth Magers, London

One of the world's most famous rooms is not all it seems in Thomas Demand's latest work

In February 1962, Jacqueline Kennedy, criticised for over-spending, took Americans on a TV tour of the White House. Opening one door, the First Lady whispered to camera, "This is the Blue Room." Then, after a thoughtful pause, "It's ... blue." It is a moment Thomas Demand might relish, although he has gone for shape rather than colour in his new works on the Oval Office.

If you don't know Demand's name, then it may be useful to ponder the German word Ordnung. Munich-born and Goldsmiths-taught, Demand has an obsession with order that verges on madness. In essence, he uses news photographs to build scarily exact, life-size paper models of dull places such as Rhineland pubs and kitchenettes. Once made and shot, these models are burned. Demand's subjects are all studiedly unmemorable, which makes their memories troubling: the pub in Tavern was the scene of a child murder, the kitchenette in Küche Saddam Hussein's. Hannah Arendt's line on the banality of evil rings in your ears.

The question that hangs over Demand's work is: why? Why go to the trouble of building a hugely complex model – choosing different types of paper to emulate ivy or linoleum or carpet exactly, cutting out endless shapes with scissors – only to destroy it? A second question is: where? Where, in this process, does Demand's art take place? In the making, in the model, in its destruction, or in its photographic remains? Somewhere in the immolation of Demand's paper Götterdämmerungs is the history of history itself – the way we absorb images unthinkingly, then unthinkingly file and forget them. All that is necessary for evil to triumph is not, pace Burke, that good men do nothing. It is that they believe their eyes.

Which makes the subject of Demand's latest suite of five works, Presidency, something of a surprise. I suppose there is a more instantly recognisable room than the Oval Office, although I can't think what it might be. No anonymity here, then; yet, for all its fame, the room is an enigma. The White House is white and the Blue Room blue; the Oval Office is the Oval Office because it's ... oval. Within its famously elliptical walls are made decisions that affect our lives and could, potentially, end them. Yet we know nothing more of the room's meaning than its shape, a geometric certainty that covers all other uncertainties.

At the heart of Demand's work is a paradox. No one could be more forensically exact than the 44-year-old German, no images more truthful than his. And yet they are lies. The closer to reality they appear, the more they fool you, the more dangerous they become: the shadows on the fake White House windows are made by real fake sunlight shone through real fake trees. Here, pre-eminently, is evidence, and yet the facts, painstakingly assembled, do not add up to fact. In one Presidency picture, we find ourselves looking at the presidential desk, a close-up view oddly devoid of information: the only things visible on it are a folder and a pad of paper, the former closed and the latter blank. In Demand's retelling of the Oval Office, identifying features are erased: the president's seal from his pennant, faces from family photographs. All that remains is the room's ovality, which we knew anyway.

The subtext of this is that the world's best-known space is also its most secret. (Is that blurry red object on the president's desk the atomic button? Does such a thing exist?) Public transparency – and, by inference, the democracy that calls for it – is shown to be sham, political truth an unending game of mirrors. Demand's works are not quick to make, and it seems clear that Presidency's unveiling must have been timed to coincide with the recent US elections, whatever their outcome. That last is quite a caveat: if there is general rejoicing at Obama's victory, Thomas Demand appears not to be part of it. Coming from a country that elected Hitler by popular vote, this may be understandable.

I'll make no bones about my admiration for Demand's art, nor about finding this latest example of it mildly disappointing. For his work to succeed, we must both want to believe in it and know that we are being fooled. Neither can exist without the other. Perhaps because the Oval Office is so well known a space, we never really feel that its Presidency double is anything more than a paper model – the presidential chair is too clunky, the pile of the carpet too coarse. From this we can deduce some general lesson about falsehood, but not that brilliant lesson taught by some of Demand's earlier work. The really worrying thing about Tavern and Küche is we joined in their deception, were willingly complicit in their lies. That doesn't happen in these new pictures, although you'd be crazy not to see them even so.

Sprüth Magers, London W1 (020-7408 1613) to 17 Jan