Jonathan Coe a considerable novelist and The Rotters' Club is an aberration, an aberration with a sequel promised (to be called The Closed Circle), which will take up the story in the late 1990s. The action of this first part starts in 1973 and covers half-a-dozen years, running through the administrations of Heath, Wilson and Callaghan, and ending on the day of the election which brought Margaret Thatcher to power. The main characters are pupils at a direct-grant Birmingham school, King William's in Edgbaston, which is both egalitarian (parents pay no fees) and élitist (entrance exam).

There's a frame to the tale, in which two young people meet in Berlin in 2003, and one of them tells the story to the other, but it's an oddly self-defeating device. If Coe acknowledges the help of a dozen or so books for his reconstruction of a period that he remembers (born 1961, he is a contemporary of his adolescent characters), it's hardly possible that young Sophie, a child of the Thatcher years, could improvise the whole thing with such command of detail, minutiae, for instance, of prog-rock bands thrown out of fashion like so many genteel Rattigans by the Angry Young Men of punk. Her stylised hesitations last only a page or two, and after that it's hard to remember the point of view from which this narrative is supposed to emerge.

The idea of using a school as a microcosm of the outside world isn't new, the most celebrated example being Lindsay Anderson's film If..., in which the conflicts of the 1960s were memorably rehearsed. But there's more than enough material in the 1970s to power Coe's story. There is the smug meritocracy of the prefects, for instance, but the school contains darker cabals, more ominous élites. There is tension between the school's two star athletes, who also share subjects academically: noble Richards, the only black pupil, and the rancorous Culpepper. When Richards wins the role of Othello in a school play, Culpepper takes no part in the production, but nature has already cast him as Iago.

The school-as-microcosm idea, though, works best if the larger world doesn't feature, while, in fact, Coe is constantly bringing in wider issues. It's as if his research into the period has made him burningly aware in retrospect of everything he didn't register at the time, the teenage cluelessness well illustrated in a scene where two schoolfriends are unable to answer each other's elementary questions about current affairs ('Why is Berlin divided, anyway?' 'And why's it called Watergate?' 'Why's petrol got so expensive?' 'Why do the IRA go round killing everybody?'). But it hardly helps his scheme to fill in the blanks, by making the father of one of the schoolboys a shop steward at British Leyland's Longbridge plant, necessarily one of the first to feel the class war changing up a few gears, even before Thatcher.

The first section of the book leads up to the bombing of the Tavern in the Town in November 1974, to the very moment of detonation. The family of the book's central character, Ben Trotter, suffers directly, but the narrative skips 18 months at this point and makes only the most gingerly subsequent approaches to the damage done. Ben had a religious experience a little earlier, a miracle, no less, involving the providential appearance of some swimming trunks, but we don't learn how his faith is tested by arbitrary horrors.

In place of the agonies of 1970s terrorism, we get a reported encounter, on the Trotters' family holiday in Denmark, with an elderly Jewish couple with tragic memories of the war. Ben is reading Tom Jones at the time and pointed reference is made to an episode in Fielding's book, a 'curious, lengthy digression which seems to have nothing to do with the main narrative but is in fact its cornerstone'. The reader is nudged here to take this section in the same spirit, but it's an effort, and the suggestion made here and elsewhere that there are some moments so perfect they stand outside time, specifically, that the pub bomb detonated too late to destroy a moment of absolute happiness, seems evasive and sentimental.

The tone is uneasily comic or, at least, non-serious. It isn't just Ben's conversion that seems curiously not to touch him - other characters also undergo rites of passage that make no difference. One aspiring rock journalist up in London for the weekend finds himself exposed in short order to the Clash in concert and inventive sex with a posh, part-time punk called Ffion Ffoulkes (who whinnies: 'Isn't this topping?' in the act), twin bombshells he takes pretty much in his stride.

Some characters exist only on a caricatural level, even if their experiences are dealt with at some length. So Sam Chase, father of another King William's pupil, decides to win back his wife, who is bewitched by the absurdly lyrical overtures of the art teacher, by enlarging his vocabulary. His crash course in eloquent expression is recounted at length, without ever becoming more than a flat comedy situation.

Even Ben Trotter comes in for some of the same treatment, in a misconceived episode of farce when he is newly a prefect and trying to make a good impression. It's the sort of routine that might have been written by Tom Sharpe at the time the book is set and leaves a residue of resentful incredulity (why would the chief master's wife remove her artificial hand at a social occasion in the first place?).

Strangely, though, the tide can flow the other way, with a minor character taking on an arbitrary depth. So Sean Harding, the school's prankster, turns out to be a devotee of Vaughan Williams, like Ben Trotter, as we learn with equal surprise. The Vaughan Williams motif accelerates from 0-60 in barely five pages, from nothing to everything, and gives birth to a fascinating description by Harding of the English as violent and melancholy - 'We repent afterwards... but first we do... whatever has to be done.' Nothing follows this up. Themes sprout and replace each other like generations of mushrooms and leave as little behind.