The Pregnant Widow, By Martin Amis

Eaxctly halfway through Martin Amis's novel about young minds and bodies who sink or swim in the sexual revolution of 1970, its protagonist enjoys a quiet afternoon by the pool. Keith Nearing, almost 21, a smooth-tongued but socially insecure adopted child and literature student, is spending a fateful summer in the Italian castle of grander friends. Both his level-headed girlfriend Lily and the aristocratic bombshell Scheherezade, new target of his rampant erotic ambitions, have left on a trip. And he has yet to come to grips with Gloria, an enigmatic Scottish adventurer whose vanguard role in the bedroom wars as an archetypal phallic woman (a "cock" incarnate) earns her the nickname of "the Future".

Keith, at rest as Amis the bustling and nervy stylist seldom allows him to be, watches while "the light began to change, as a cloud hurried sideways to shield the modesty of the sun, and a shape like a dark starfish came writhing up from the depths. Only to meet its original – a falling leaf – as the surface changed from glass to mirror".

In this chapter, "The Turn", a presiding motif of metamorphosis (Ted Hughes's versions of Ovid punctuate the novel) reveals Keith and his era on the cusp of a vast change. According to the older Keith, it will set a creed of instant gratification against the old laws of love, enslave rather than free women ("The boys have won. Again.") and bleach the sexual act of "all the ancient colourations of significance".

Yet the novel, like the castle pool, works equally as a glass and as a mirror. Subtitled "inside history", it aims to document the moods of a pivotal moment via the erection of an isolated stage for talk and for trysts – a drama with "the unities of time, place and action". These wayward children of wars, both hot and cold, will start to cut sex loose from commitment and so, for the most part unwittingly, usher in an pornographic age of sham and sheen when surface will "supersede essence".

We look through a screen at this social history; but also at a reflection of the ageing Keith's hindsight. Via brief leaps forward and a leisurely finale, we glimpse his future face and fate – and those of his summer chums as time takes their arm (or grabs their collar).

Out of this spell of "sexual trauma", some will strike lustily out for the safe shore of maturity. Others, notably the chaotic and abused figure of Keith's sister Violet, will drown. In Keith's chronicle of the sexual insurrection, "the spirit of the times" proves a tonic for men and a toxin for women.

The Pregnant Widow has already secured such a firm niche as a contentious novel of ideas that we can lose sight of the way it frames two panels of an individual life. A mature narrator looks back on the battlefield of desire in anguish, if not in anger. Trust the tale, not the teller, DH Lawrence said. (Keith is speed-reading his way through landmarks of the English novel, and their mixed notes on the rules of attraction – from Clarissa through Pride and Prejudice to Lady Chatterley's Lover – add counterpoint and perspective to the malarkey in the castle.) Beyond a downbeat diagnosis of the malaise that grew from this "velvet revolution" lies a fully fictionalised account of one man's "crisis of mortality", and the pall that it casts over once-golden memories.

Age and time lay rough hands on Keith, as they do on so many later Amis heroes. If this sequestered world of erotic experiment brings his early Dead Babies to mind, then the background hum of entropy – the slow drag of disorder within a body or a culture that will push it towards a standstill – repeats themes from The Information, London Fields or Einstein's Monsters.

With its attention to tectonic shifts within cultures and systems, its discursive, mannerist debate within a small closed world, its focus on an alien environment as the forcing-house for change, The Pregnant Widow also underlines Amis's credentials as a particular kind of science-fiction writer. (That interest his father, Kingsley, also shared.) For all Keith's loyalty to "social realism", his tarnished idyll works like a spaceship setting where futures bright and scary may unfold. You might even imagine this novel as a pastoral variation on Star Trek: The Next Generation, except that it could be retitled with another word that ends in "k".

Amis the moral and historical speculator is engagingly open to dispute; Amis the comic artist in prose remains a true master, and a model. As a virtuoso syncopator who lends a hit of rhythmic or lexical pleasure to every snatch of speech or scene-sketching paragraph, he sounds as sweet as ever. Entropy has not yet cramped his style.

As always, his gleeful repetition of riffs and runs dusts a little joy over every page. The mangy dog in the village pet shop who might even be a rat; the ever-rising stature of the lady companions who join the gallant, dwarfish count Adriano; the house guests' fixation on the sexual undertones in Jane Austen: Amis's comic loops and circuits buzz without remission. Indeed, The Pregnant Widow can sprawl and stray. One quip from Pride and Prejudice that may apply is Mr Bennet's line about delighting us long enough. But delight us Amis does, and as few can. In his poisoned paradise, the "rebel angels" sing in their self-made chains.