In the mid 1960s, Fred Friendly, friend of and producer to the legendary newsman Ed Murrow, visited his boss at CBS, the no-less legendary William Paley, and fell to arguing about the network's profitability. "How much money did CBS make last year?" demanded Friendly. Told it was $50 million, Friendly retorted: "That's enough." Wrong: in the next few years, it doubled again. For journalism, a rude awakening was in store: the media is business, and business is business.

In the past 50 years, no figure has been so closely identified with this shift as Rupert Murdoch, the stateless, weightless, desiccated calculating machine of the era of mass communication. Now 77, an age where most men of his accomplishment are sitting to have portraits painted or dictating self-justifying memoirs, he has settled for a cross between the two: sitting, for 50 hours, to share his memories and musings with Vanity Fair's Michael Wolff, and encouraging others in his circle to a similar candour.

Quite why, who can tell? Murdoch is mercurial, Wolff relates, and his mood swings are frightening because "you don't quite know what his mood is, other than to sense that his attention and humour and purpose have rather shifted." Wolff suspects that Murdoch is feeling pleased with himself - sure he has done something significant in his recent takeover of Dow Jones & Company, publisher of the Wall Street Journal, but perhaps not quite sure what. But, for all his dwelling on Murdoch as a stranger to introspection, Wolff is curiously lacking in the same quality: an urbane New York liberal man-about-town, a wannabee communications entrepreneur himself and a big-name writer who rolls phrases as fat as figurados, he accepts entry into Murdoch's circle as no less than his due. The result is a study in which the biographer's ego is so much larger than the subject's that you are never quite sure whether judgements are passed after deep consideration or merely because they echo satisfyingly round Wolff's skull.

Even the structure of The Man Who Owns the News: Inside the Secret World of Rupert Murdoch (Knopf, 446pp; $49.95) is devised with Wolff's writerly preferences in mind. His speciality in Vanity Fair is inside stories of billion-dollar deals, fetishistically embroidered with fly-on-the-wall detail. Over the narrative of Murdoch's life, then, is stretched the gradually unfolding tale of the Dow Jones takeover - or, actually, it more often feels that the deal is punctuated by digressions into the life. The effect is the very opposite of seamless, not least because the life is so crudely compressed (Wapping in three paragraphs, no Super League, no One.Tel), while the deal-making sequences are gussied up with ruminations like: "He tends to create a disturbance, or pick up the tremulous motion of a disturbance, that in the chaotic motion of the atmosphere becomes amplified, eventually leading to large-scale atmospheric changes ... or some such." And: "Nothing - even nothing itself - goes on forever. A lack of movement is itself odd and disturbing, and if you're finely attuned to these sorts of things - stasis where there should be progress - it suggests its own sort of opportunity." Up to a point, Lord Wolff.

This concentration on the Dow Jones deal is justified in the deus-ex-machina concluding chapter, where Wolff argues that Murdoch personally remakes himself through his business activities. This savours of post-hoc rationalisation. You could argue just as forcefully that the Dow Jones takeover - the exploitation of a feeble, fissuring family - was an old-fashioned Murdoch set piece. Indeed, at other stages Wolff seems to offer quite opposite propositions: that Murdoch's relative failure in American newspapers is explained by a stubborn, holus-bolus importation of British tabloid culture; that the puritanical Murdoch deplores superficial, sybaritic Hollywood. Mind you, this deal-as-personal-therapy hypothesis does not diverge from reality so sharply as the assertion that Murdoch ended the 1980s having been transmogrified from a workaday mogul into "a practitioner, a connoisseur, a lover of business itself" committed to "going wherever the transforming nature of business ... takes him". In fact, weighted down by Sky in Britain and Triangle in the US, Murdoch ended the '80s hanging by his fingernails from a financial window ledge; only a dotcom dilettante like Wolff, a happy habitué of the world of unearned billions, could toss off an opinion so casual.

Wolff would presumably argue that he is chiefly concerned with the essence of Murdoch rather than the bottom line of News Corporation. Yet his starting point is really that the two are indivisible. Early on, he offers us Murdoch as "a new sort of business guy", devoid of interests outside work, dwelling in a permanent present, animated by "a sort of autism or fanaticism". In fact, this is neither an original nor a useful assessment. It's almost 25 years since George Munster, in A Paper Prince, called Murdoch "a person without a hidden self" who "is what he does". William Shawcross's verdict, at the end of the last major Murdoch biography, was bleaker still: "Beyond the empire, he has no interests apart from his family, to whom he is devoted. He finds it virtually impossible to relax. He does not read books, nor listen to music, nor enjoy museums ... He does not sleep well. In his early sixties he is still a man possessed - and lonely." If anything, Wolff's Murdoch, a husband and father again in his seventies, seems rather jauntier than this, yet still he is cast as a riddle inside an enigma inside a conundrum: "Disconnected, physically as well as emotionally. Everywhere but nowhere. Not part of anything. Just a man with a phone." And. So. On.

Because this thesis has to be served, furthermore, there are times when Wolff seems to go out of his way to make Murdoch less interesting than he actually is. He describes how, 40 years ago, Murdoch - after running extracts from Christine Keeler's memoirs in News of the World - was lured into an interview with David Frost on London Weekend Television. Murdoch, offering a view of Britain as hidebound and insular, was vigorously challenged by the self-consciously self-made Frost: "That's an Australian view of England - it really is, you know. I mean, it doesn't work that way anymore there, you know. It really doesn't. I mean, of course there's a lot of daft old-school ties in this country and so on but it doesn't work like that - the establishment are not as well organised as that." At the time, Murdoch offered only the magnificently laconic reply, "You reckon?" With Wolff, he was a good deal more forthcoming:

I swore I would never, ever have anything to do with Frost on any level in any way and ... for at least twenty years I never spoke to him. He'd be all over me at parties, "Oh, Rupert ..." I've never had a one-on-one with him since and I've always been very cold with him ... I thought he was such an arrogant bastard, a bloody bugger ... I feel like saying I'll get the bastard one day, but he'll die before I get him.

For some reason only the last line of this pithy gripe makes the actual text - the rest is entombed in an endnote. Nor is this the only example of Wolff apparently ‘burying the lede'; it's almost as though a too-colourful Murdoch would cramp the writer's style. 

On the subject of Murdoch's furthering of his business interests through politics, Wolff offers that his subject has been shaped by the involution of Australia's political networks, having had "from an early age, access to everybody who counts in the country" and believing consequently that "nothing happens without a systematic program of influence". He also proposes that Murdoch's politics, famously and rigidly of the Right, are more a means of "connecting to somebody", a barometer of temperament as much as ideology: "Are you sentimental or are you realistic. Are you a basic sort or are you fancy?" Murdoch, he insists, warms chiefly to "a lack of equivocation, a firm declaration, a clear identity, a fundamental compression".

This undergirds the headline assertion that Murdoch's politics, under the influence of his third wife, Wendi Deng, have lately grown more liberal: that he is repelled by Fox News; that the purchase of Dow Jones was geared to "looking for better company" than the crude agitprop of The O'Reilly Factor et al. A strange world, this, where one tilts Left by buying the Wall Street Journal. Again, you wonder whether the author is seriously interrogating Murdoch's motives, or describing what a wealthy east-coast intellectual with liberal pretensions but capitalist instincts would do were he in Murdoch's place. And, in the end, Wolff is so post-ideology himself that he can't be bothered with serious questions about the place of a free press in the modern polity, whether news should be judged on the same basis as entertainment, how long the media can claim a quasi-institutional status when its managers can think no further than hurdle rates of return, and how much is enough where media profits are concerned. Perhaps Murdoch doesn't know; it's a pity Wolff doesn't care.