Sarah Thornton guides us through seven different scenarios in the contemporary art world: an auction, an art school, an art fair, an art prize, an art magazine, an artist's studio and an art biennale. We learn what's in everyone's offices and studios and what they eat for lunch (salad in the Turner prize inner sanctum where the jury meet to decide the winner). The nosiness is compelling. Thornton is a camera.

Unfortunately, she's not a seer, she's without a vision of how things could be different. Like the art world itself, she assumes only a loser would challenge the system. I'm not saying it isn't a fun read. The reporting is amazingly thorough. But where's the attitude?

In New York the publishers of Artforum chat up a storm without revealing anything important about the business they're in. Sometimes this seems to be because they're a bit snaky and sometimes because they really do have the innocence of Winnie the Pooh. When Tony Korner tells Thornton the last thing Artforum would ever do is follow the market, he's being a bear with little brain. He believes what he says. But you'd expect Thornton to tell us where logic falls down in this account of an art magazine that's sometimes two inches thick with expensive ads paid for by the same galleries whose shows are reviewed in its pages. She doesn't do it because she's in the business of taking art world people very, very seriously.

Back in London an installation by a Turner prize artist that deconstructs reality TV, and mixes obscurity with mawkish sentimentalism, as much current conceptual art tends to do, is described as "moving" and "subversive". At least we rarely fail to hear what people are wearing and what their hair is like. "Buddy Holly glasses" on curator Matthew Higgs, "only light mascara" on Turner prize-winner Tomma Abst, a "no-nonsense white shirt hanging loose over an Agnès B skirt" on women's studies lecturer Leslie Dick.

I was gripped (for the wrong reasons) by the chapter on Japanese artist Takeshi Murakami, whose global operation is like Ruskin's worst nightmare - capitalism that not only destroys the soul but also creates a new world in which having a soul is the equivalent of being born a leper. The work is cartoon pornography - manga clichés - in the form of paintings, sculptures and prints, plus a Louis Vuitton bag. François Pinault, the multi-billionaire art collector who has a private museum in Venice and owns Vuitton, has commissioned some cartoons on a vast scale from Murakami. The work is stalled for technical reasons. Solemnity marks the moment. Thornton reports a line of Murakami's business people - "Takeshi being late for Pinault is like Michelangelo being late for the Pope!" - as if it were a real thought instead of hysterical sales-talk.

In a chapter on the Turner prize, she writes that "the press never tires of the question 'Is it Art?' and finds it impossible to resist sex jokes". On the same page she makes two sex jokes herself; describes a Tate curator's outfit in sexist terms; and then goes on to deny the seriousness of half of Rebecca Warren's Turner prize-entry sculptures by calling them "more pre-school than art school". It's an odd moment. You want her to be far more undermining, but when a bit of contempt gets out accidentally it's jarring.

Thornton has a BA in art history and a PhD in sociology, and she says she takes an anthropological approach to her material. And yet the style of Seven Days is indistinguishable from standard middlebrow journalistic reporting - description mixed with interviews, both oiled with regular chatty interventions. These have two modes. A bit brassy: Thornton suspects Warren's boots are "just one pair in a considerable collection of trophy footwear". And light Dickensian: summarising the repressed minimalism of Nicholas Serota's desk, she quips: "paper is evidently forbidden to accumulate into a stack".

Thornton doesn't deconstruct Serota's performance in his interview but lets us know in an ethnographic, David Attenborough near-gorilla whispering that she's thrilled to be in his office. (He wears a "muddy asparagus-green tie".) The scene stands out in the book because so many of the other players imitate loony Californian-speak or actually are Californian, while Serota is incredibly British. It's a hoot to witness him dodging feminist flak from Thornton, stitching up the other members of all the Turner prize juries over the years for the low chick-count among the prizewinners; not to mention making it absolutely clear that the jury would never remotely consider taking nominations for the prize from the ordinary public, while somehow sounding as if he's saying the exact opposite.

Curators on a perpetual global party circuit who think of themselves as edgy thinkers; pampered artists desperate to be awarded the Turner prize whose installations are supposed to be about profound anarchy - Thornton gets to the heart of the problem of art-culture, which is that art has become trivial, whereas in previous eras it had some dignity. But she's too wrapped up in playing a role to realise it: she doesn't nail the problem but acts it out, and so ends up perpetuating it.

 Matthew Collings's This Is Civilisation is published by 21 Publishing

The title subtly suggests the idea of a quest. Seven days to save a masterpiece for the nation! Seven days to rescue Damien Hirst's reputation! But in fact Seven Days in the Art World is only, somewhat less excitingly, what it purports to be: an account of seven disparate days spent in the excessive and increasingly loopy world of contemporary art. Its author, Sarah Thornton, a 'sociologist of culture' whom the Daily Telegraph once described as 'Britain's hippest academic', visits an auction and a biennale, a prize giving, an art fair and an artist's studio. She also, more weirdly, hangs out at Artforum, a New York art magazine, and attends a student seminar at the California Institute of the Arts in Los Angeles.

The result, from her publisher's point of view, is an 'insider' guide to the shadowy types who make, market, sell and buy art. Thornton, however, appears to believe that she has dished up rather more than this. At the end of her book is a brief note in which she explains her methodology. 'Ethnography,' she writes, 'is a genre of writing with roots in anthropology that aims to generate holistic descriptions of social and cultural worlds. Its main research method, "participant observation", is a cluster of qualitative tools, which include first-hand experience of the environment, visual observation, attentive listening, casual interviewing and analysis of key documents.' Well, who knew? The rest of us call this journalism.

This particular ethnographic odyssey, according to a rather pert video of Thornton on YouTube, took her five years to complete, during which time she interviewed, formally or informally, 250 people, among them Charles Saatchi and Larry Gagosian. Unfortunately, this research is not always apparent in her minute-by-minute narratives ('2pm: time to meet an Italian collector for lunch... 7pm: I'm stuck in slow traffic on my way to Chelsea'). The likes of Saatchi, an extraordinary and fascinating case study when it comes to modern collecting, and Gagosian, a gallerist who is known to protect his artists' stock with a fierceness you might ordinarily only expect to find on a Wall Street trading floor, are not quoted at length in her book, presumably because they insisted on speaking off the record (several collectors who are quoted are given made-up, Tom Wolfe-ish names like Dwight Titan and Sofia Ricci). In which case, why mention, in your acknowledgments, that you talked to them at all? No one likes a tease.

Still, Thornton has bagged a few big beasts. Nicholas Serota is here, in all his inscrutable, white-shirted glory and Philippe Ségalot, the art adviser who oversees the collection of François Pinault, the owner of Christie's, Gucci and Château Latour. 'Buying is an extremely satisfying, macho act,' he tells her over fish carpaccio and sparkling water.

Naturally, most of these people are pretty circumspect about what they say to Thornton, however attentively she listens. Disappointingly, the Rubell family of Miami, the owners of a fairly significant collection of contemporary art, won't let her follow them round Art Basel, the most important art fair in the world: 'That's like asking to come into our bedroom!' Occasionally, though, someone says something pleasingly dumb, revealing or both. At an auction at Christie's in New York, a well-known collector, Juliette Gold (not her real name), incisively analyses why the bidding on a painting by Warhol, Mustard Race Riot, has been somewhat stuttery: 'It's a great historical piece, but it's not a very appealing colour and it's too large to hang easily in one's home.'

At the California Institute of Arts, where sessions of group criticism last so long that participating students take naps, get on with their knitting and order in pizza, a student tells her: 'Creative is definitely a dirty word... it's almost as embarrassing as beautiful or sublime.'

When she visits the foundry where Oval Buddha, a huge sculpture by Japanese artist Takashi Murakami is nearing completion, she watches curator Paul Schimmel clap eyes on a piece he will shortly put in a Murakami retrospective for the very first time: 'It's either a disaster waiting to happen or it's... brilliant,' he says, gazing up at the 18-foot-high work ('a Humpty Dumptyish' self-portrait, according to Thornton). Then he remembers what he's about. 'In terms of showstoppers, I got lucky. They'll be praying to this thing in 500 years!'

The trouble is that the hope of the odd daffy quote is not enough to keep you reading. Newspapers and television are crammed with stories about art, from the latest crazy auction-house prices to the wilful silliness of the next contenders for the Turner Prize (Thornton devotes a whole chapter to the Turner Prize and, for the record, she was able to elicit no more useful information from the 2006 winner, Tomma Abts, than anyone else).

To write a successful book about this world, a writer must bring something extra in the way of insight or argument. What Seven Days in the Art World lacks, fatally, is a point a view; a sense of investigation as well as observation; a little polemical verve to pull the reader along. Thornton never adequately explains how an artist comes to be considered worthy of critical or commercial attention. I still don't know why, exactly, the likes of Dwight Titan hanker after Jeff Koons, though Roberta Smith, the powerful and waspish art critic of the New York Times, brilliantly sums up the art of criticism itself when she says: 'You put into words something that everyone has seen. That click from language back into the memory bank of experience is so exquisite. It is like having your vision spanked.'

Does ethnography require its practitioners always to favour comprehensiveness over judicious selection? Perhaps. Thornton describes everything: every lunch, every fashion statement ('a petite curator in low-rise black jeans that revealed a hint of midriff briefed the crowd'), every object ('he stared into a well-used cut-glass ashtray') - but never for any other reason than to prove that she was there. A lot of non-fiction being published at the moment seems to be all style and posturing and no hard graft. This book is all graft and not a lot else.

What, I wonder, does Thornton really think about what money has done to art? Does its corrosive influence ultimately matter? Most important, when, if ever, will the bubble - so shiny and so seemingly impenetrable - burst? These are the questions I wish that she, or someone, would try to answer.