Barack Obama: The Making of the Man, by David Maraniss

Can an exhaustive history of the president's cosmopolitan past explain his present?

There don't seem to be any reliable figures on how many Americans have ever travelled outside their own country, speak any foreign language, or even possess passports – but rival guesstimates agree that these are very much minority attainments. Even among elites, there's a degree of insularity almost unmatched elsewhere, except perhaps for the Chinese. More startling is the extent to which US politicians, including presidential candidates, have seen and used parochialism as an asset, a positive value to be proclaimed and indeed exaggerated.

Actually, among modern presidents, only Harry Truman really came close to fitting the small-town, Southern or Midwestern ideal; but almost all others have pretended to it. Reagan's or Dubya's crass ignorance about global affairs – sometimes genuine, sometimes slyly assumed – was not the least among the roots of their popularity. Against that backdrop, the cosmopolitanism of Barack Obama's family and youth in Hawaii and Indonesia is truly remarkable, and the artfulness of his selective use of it, combined with its semi-denial, readily explicable. So too perhaps is the strenuousness of his early efforts to "become African-American", refashioning himself towards an identity which often seems even more inward-looking than other forms of Americanism, if only because economic disadvantage has meant blacks are even less likely to be widely travelled.

Obama's own efforts – not least in his bestselling memoir Dreams from My Father – have thus contributed almost as much as enemies' attacks or the ambient pressures of American racial obsession to focusing attention on one of the least important or interesting things about him, the colour of his skin. David Maraniss's vast chronicle of the President's family and early life tries to challenge such stereotyped and infatuated perceptions, while also often reading like an extended commentary on Obama's own writings. For all its insight and sharp intelligence, and despite – or because of – its enormous length, it is only a partial success in that.

The book has a strange combination of gross excess of detail on some themes, frustrating sketchiness on others. Also, Maraniss never really resolves, though he very often repeats, either of his key interpretive dilemmas. One is about how far, or in what ways, Obama's background makes him an outsider to some imagined American mainstream, with either the particular insights or the special handicaps which such a marginal position might endow. The other is over whether tracing family histories and youthful experiences really tells us much about the mature career and views of someone who is, as Maraniss stresses, apparently so thoroughly self-made as Obama today.

Maraniss's third key theme is rather less significant, though critics have fastened on it: how far are Obama's own writings an accurate account of his early life? The answer is, unsurprisingly, often not very far at all. Dreams from My Father engages in a fair bit of compression and selectivity, airbrushes a few small embarrassments, slightly exaggerates both his father's accomplishments and perhaps his own, and so on. But Maraniss never actually catches his subject out in anything like a direct lie or a total fabrication – not that this highly sympathetic biographer shows sign of having wanted to do that.

Obama's references to childhood friends, relatives, or early girlfriends emerge as models of tact and discretion, qualities which those who agreed to talk to Maraniss have reciprocated. Among the book's most revealing informants is the partner in young Barack's most important love affair, Australian Genevieve Cook. Her diaries and memories are keenly perceptive, but also almost entirely positive and affectionate.

The book's sometimes over-detailed narrative is rarely matched by penetrating analysis. Despite stressing how important the local peculiarities of Kenyan, Indonesian, Hawaiian and indeed Kansas politics and cultures were to the making of Obama, Maraniss's commentary seldom goes beyond bald chronicle or ethnographic cliché. Obama's own mother, a talented scholarly anthropologist who worked in Indonesia, would surely have done far better on this front had she lived longer.

We learn quite a lot about what Obama thinks of himself, much less of what, or how, he thinks about the world. Maraniss tells us more about young Barack's musical loves (some, like Bob Marley, might have had a real political influence, while others – Earth, Wind and Fire! – were perturbingly insipid stuff) than about what or how he read. Maraniss's philosophical asides can sound emptily portentous: "That is how history works…Along with the rational processes…there come seemingly random connections that spin out… unintended consequences."

Despite such minor excesses and more serious omissions, this is an engrossing and sometimes rousing book, giving a more intimate picture of a serving President than any other writer has done. Little less compelling are the portraits of his parents, both the utterly admirable mother Ann Dunham and the far more flawed, abusive and self-destructive Kenyan father, Barack Sr. There are multiple incidental revelations, many of them crying out for more probing into how, if at all, they might influence global politics today: for instance, the unexpected fact that so many of Obama's closest student-era friends were Pakistanis.

Most of young Barack's (or rather Barry's) friends and acquaintances seem, in one way or another, to have been positively impressed by him. Few, though, were overwhelmed, or detected the kind of ferocious drive to succeed which, say, the similarly aged Bill Clinton always displayed. The charismatic, glamorous, stunningly eloquent Obama who suddenly hit the world stage in 2008-9 was, clearly, formed only well after his mid-twenties, where Maraniss's story stops. The strongest prefiguration of that man to be found here is perhaps in the brief fragments of Obama's own early, unpublished writing which Maraniss quotes.

These, no less than Dreams, hint at a literary skill and intense self-awareness suggesting that, however the man's future reputation as a President may fare, we will surely one day have from him the best-ever presidential memoirs.

Stephen Howe is professor of the history and culture of colonialism at Bristol University.