The Rub of Time by Martin Amis: has age watered him down?

Writing about Saul Bellow – the subject of several star-struck pieces in this typically glorious, typically enraging collection – Martin Amis notes how, even at 80, he was still able to "hear the thought-rhythms" of the modern world. You'd think, from the way he puts it, that Amis considers this faculty to be innate, much like the less exalted kind of hearing: either you have it (and hang on to it) or you don't.

But hearing, and articulating, those rhythms is something that Amis has worked hard to achieve, ever since he got started in the early Seventies. He is, after all, the everyman-writer who also refuses to publish "a sentence that any guy could have written".

In the novels, this tightrope act has proved hard to sustain, with spectacular successes (Money) and sputtering misfires (Lionel Asbo). In the journalism, at least when the subject hasn't been Islamic fundamentalism, the results have tended to be steadier, with Amis's ironic refinement providing an effective frame for his gleeful forays into the garish, slang-ridden here and now.

As a title, The Rub of Time is grand, and gnomic, and quite close to being the third step in a roast chicken recipe, but it starts to make sense when you read on and find that a lot of the book is concerned with getting old.

Amis touches on the theme, with varying degrees of sympathy, in pieces on pop culture (poor John Travolta), politics (is Donald Trump dementing?) and sport ("then you come to the massive emplacement of [Maradona's] gut"). Unsurprisingly, though, what he's most interested in is the unique form of ageing experienced by everyman-writers.

Amis worships Nabokov only fractionally less than Bellow – describing them, not for the first time, as his "twin peaks" – but he's excellent on where, and how, things started to go wrong in the later work.

Investigating the mysterious case of John Updike's vanishing ear, he can be ridiculously fussy (giving Updike a rap over the knuckles for using "prior" and "prime" in the same sentence); but you're also reminded of his astuteness as a reader, and his instinctive grasp of what an author's up to. Elsewhere, he describes Updike's "busy eyes... the set of the mouth (as if containing, with difficulty, a vast and mysterious euphoria)".

What conclusions do we draw? "Age", says Amis, "waters the writer down". It's a familiar sort of judgment – offhand, all-encompassing, though unusually well-supported in this case. But, as with many of the Amis laws (about men, say, or "the English"), it's hard to tell whether he really thinks it applies to him, even as he pushes 70.

In his 20s, Amis cut no slack for older writers who tried but failed to be down with the kids (Angus Wilson got a particularly rough ride). And there's an observation of his father's that clearly stuck, because he wheels it out almost as often as his own pet theories.

According to Kingsley Amis, there comes a point in a writer's life when a bunch of young guns turn up and say: "It's not like that anymore. It's like this." Amis Jr is aware of the indignities that can come with clinging on for too long. Is he ageing gracefully?

One development is that he has started editing his pieces to reflect a fairly new regard for what he calls "decorum". In his report on the porn industry, for example, a male star, originally "big-dorked", is now "grotesquely endowed". And it has occurred to Amis that if you want people to believe you are a "gynocrat", and indeed a fully grown man, you don't make your case by claiming to "believe in rule by chicks" (now just plain old "women").

The war against cliché has morphed into the war against colloquialism – sometimes for the better. Elsewhere, though, we find eruptions of genuine, presumably unintended fogeyishness. Mocking Trump's idiolect (not the hardest job around), Amis wonders if a woman has ever been known to say "I am what I am", having apparently reached 2016 without coming across Gloria Gaynor.

Meanwhile Jeremy Corbyn, along with his bad A-levels, "has no grasp of the national character" – the kind of jowl-shaking harrumph you might expect in a heavy-handed parody of Amis Sr. There are times, too, when Amis is just plain wrong. Is the "thirst for fame" that characterises "our era" (a long-standing peeve) really an explanation for global jihad?

The paradox, however, is that Amis's best stuff has always required a certain lack of self-consciousness. While his insistence that writing is a largely "unconscious" process – an idea proffered at least three times here – can get tiring, it does help to explain the singular pleasures of his style: those bracing verdicts, those flashes of perception.

Donald Trump wears "an omelette of make-up", Mitt Romney "resembles a long-serving porn star" and Jack Nicholson's grin says: "You're even dumber than you think I think you are". Russian novels are "dementedly robust".

In the American Midwest "Everyone is called Johnson. And everything is called Johnson. And everywhere is called Johnson: streets, forts, bridges, creeks".

When Amis ponders his own decline – physical, rather than literary – there's a double display of humility. He hands over to his son, who says of a football match they watched together: "In the 63rd minute, Paul Scholes scored for England. And in the 65th minute, Dad leapt to his feet".

Very few writers can surprise and delight in the way Martin Amis can. There may be pratfalls to come, there may be breaches of decorum, but that ear for the thought-rhythms will have to get a whole lot tinnier before I stop reading him.

The Rub of Time:  Bellow, Nabokov, Hitchens, Travolta, Trump. Essays and Reportage, 1994-2016 ?

368pp, Jonathan Cape, ￡20, ebook ￡9.99. To order a copy of this book for ￡16.99, call 0844 871 1514 or visit books.telegraph.co.uk