So he builds elsewhere. His buildings, which always favour provocation over conventional notions of beauty, are always intriguing. There is a clutch of good houses - one of which, in Bordeaux, comes close to the sublime. There is a dance theatre in Holland, not to mention the entire unreal district of Euralille in Northern France: a theoretical masterplan that, rather unexpectedly, got built. He is building a bit in America, he has just won a concert hall in Oporto. Once he looked set to be purely a teacher and writer. Now, he is one of the rarified globe-trotting elite of in-demand architects, most of whom you know he despises.

All pictures: Bordeaux house, 1998

Were it not for the evidence of his buildings, you might conclude that Koolhaas lacked substance. He can fill any hall, anywhere, any time, with crowds of people come to pay homage to his aphorisms - which seem to be mostly about the helplessness of architecture in the face of global economic and political forces. He is essentially a voyeur, observing and interpreting the forces of change, from Manhattan to Shanghai. He offers no ready solutions and resolutely refuses to make predictions. That way, of course, he cannot be proved wrong.

At a recent London lecture, when a tanked-up student asked him what football team he supported, Koolhaas paused for a ludicrously long time before replying: "That depends." A fairly typical response: can one conclude that Koolhaas thinks too much, and knows too much, to be truly effective as an architect, let alone a football fan? Then again, most architects can hardly write their own names. Koolhaas, the one-time scriptwriter, is ahead of the game here.

After the lecture, discussion or whatever, the faithful queue to buy his book. It is a very big book, about the size and weight of Who's Who, with a highly designed silver cover, and it has a particularly fine title: S,M,L,XL. Standard clothes sizes, in case you hadn't twigged, applied to buildings, among them Koolhaas's own. The creation of these, and the abandonment of many other projects, is given an epic flavour. The subtext to the book, ambitiously but mistakenly described as "a novel about architecture" is the architect as hero. Koolhaas denies this, indeed he says in terms that he and his architecture are determinedly anti-heroic, but that's not the impression you come away with. All 1380 pages of S,M,L,XL are wallpapered through the ICA's gallery as a running commentary.

It is a big seller. The biggest thing in it, fame wise, is a celebrated essay on "Bigness" as an architectural determinant. This is lucidly written, but all it comes down to is that some buildings are now so huge that there's room for lots of other architectures to happen inside their skins. This is absolutely true to the point of being rather obvious. It doesn't amount to much as a theory, you'd think - but it's the way he tells 'em. The presentation, the packaging, the air of myth and mystery, is a great deal to do with the success of Koolhaas. In this the book is like his practice, the portentously-named Office of Metropolitan Architecture or OMA.