Christopher Hitchens is living in what Philip Gould, the New Labour pollster and author of The Unfinished Revolution, described in a recent, and poignant, BBC interview as the “death zone”. He, like Gould, is terminally ill. We all live under a death sentence, however long it may be suspended, but it concentrates the mind if you are told that the end is much nearer than you would have wished – terrifyingly near. “I had immense plans for the next decade,” Hitchens said wistfully when he was diagnosed with inoperable oesophageal cancer last autumn.

There is, inevitably, an air of last things about this collection of essays, reviews and columns written over the past decade or so, a sense of leave-taking, and you read Arguably knowing that this great provocateur and polemicist will soon be silenced. Since being told a year ago that he had as little as another year to live, Hitchens’ articles have been written with “full consciousness that they might be my very last”. This is, he writes in the introduction, “Sobering in one way and exhilarating in another ... it has given me a more vivid idea of what makes life worth living, and defending.”

The epigraph to Arguably is a resonant line from Henry James’s The Ambassadors: “Live all you can. It’s a mistake not to.” The speaker is Lambert Strether, a model of Jamesian reticence and repression. But there is nothing reticent about Hitchens. He has emphatically always chosen life, and lived it all he could. “I burned the candle at both ends,” he has been saying in recent months, “and it often gave a lovely light.”

Born in 1949, he remains a recognisable late-1960s archetype, radicalised and shaped by the counter-cultural spirit of the turbulent era of the Vietnam war and the sexual revolution. (He is rather like Philip Roth’s David Kepesh: celebrity journalist, upmarket talkshow star, libertine, scourge of bourgeois respectability and conventional behaviour.)

The son of a Tory naval officer, Hitchens was educated at a minor public school and Oxford, where he became a champagne Trotskyite. As a student, he joined the far-left, anti-Stalinist sect, the International Socialists (forerunner of the Socialist Workers party), and agitated at demonstrations by day and romped and cavorted with the daughters, and sometimes sons, of the landed classes by night. He remained a member until the late 1970s and, long after that, continued to defend the Old Man, as he and comrades called Trotsky.

After university, he worked on the New Statesman, under the editorships of Richard Crossman and Anthony Howard, before he moved to Washington in his early thirties. There, after some initial struggles, he began to find his voice and signature polemical style, contributing to Harper’s and The Nation and then as a well-paid de luxe contrarian, to Vanity Fair and The Atlantic.

I once had a drink with him in the mid-1990s after we were introduced by the former Conservative MP George Walden. We were in the basement premises of Auberon Waugh’s old Academy Club, in Soho, and the air was rancid with cigarette smoke. Hitchens sat opposite me at a table, chain-smoking and drinking whisky, and he spoke in long, rolling, perfectly formed sentences as he recited, from memory, large chunks of WH Auden’s poetry. I felt battered by his erudition – can you keep up, young man!

Hitchens exuded what I thought then was a superb worldliness. His voice was deep and absurdly suave – and, in manner and attitude, he closely resembled his old friend Martin Amis, both more than half in love with their own cleverness and verbal fluency. Hitchens was engaging enough, yet I found his confidence disturbing: he knew what he knew and no one could persuade him otherwise.

An absence of doubt defines his work as a journalist and writer. His weaknesses are overstatement, especially when writing about what he despises (Islamism, God, pious moralising of all kinds), self-righteous indignation (“shameful” and “shame”, employed accusatorily, are favoured words in his lexicon), narcissism, and failure to acknowledge or accept when he is wrong. His redeeming virtues are his sardonic wit, polymathic range, good literary style and his fearlessness.

Martin Amis, in Koba the Dread, his book about Stalin and the British left’s historic reluctance to condemn the crimes of the Soviet Union and its satellites, suggests that Hitchens began to improve and grow as a writer, his prose gaining in “burnish and authority”, only after the fall of the Berlin Wall in 1989, as if before then he had been ideologically and stylistically constrained by a self-imposed demand to hold a fixed ideological line, even at the expense of truth-telling.

Until the beginning of this century, Hitchens played the role of Keith Richards to Amis’s Mick Jagger. He was the more dissolute, the heavier drinker and lesser writer, very much the junior partner in an ostentatious double-act. Amis was a multimillionaire literary superstar, “the most influential writer of his generation” in his own self-description. He wrote in the High Style, after Saul Bellow, and boldly declared war on cliché. Hitchens, by contrast, wrote journalism and was not averse to using cliché or ready-made formulation. Here he is, for instance, reporting from “Kurdistan – the other Iraq” for Vanity Fair in 2007: “Iraq as a state was always crippled by the fact that it contained a minority population that owed it little or no loyalty.” That’s the kind of awkward sentence that Amis mocks and scourges.

Yet, over the decade covered by this book, Hitchens caught up with Amis, whose reputation has been diminishing ever since the 1995 publication of The Information, his novel about two rivalrous writers, and then overtook him. It was as if their roles had been ironically reversed. Amis, in his non-fiction, instead of writing literary criticism, wrote mostly about politics and world affairs in the aftermath of the al-Qaeda attacks of September 11 2001. Hitchens did not start writing fiction and poetry but he did begin writing seriously about them for the first time – some of the best essays here are on Philip Larkin, Vladimir Nabokov and Saul Bellow, writers revered by Amis.

Hitchens writes about very few contemporary novelists with the exception of his friends (Salman Rushdie, Ian McEwan, Amis), and even fewer women (his literary tastes are “homosexual”, as he once put it). His choices are curiously old-fashioned, even schoolboyish (Kingsley Amis, PG Wodehouse, George MacDonald Fraser, Arthur Conan Doyle).

After the September 11 attacks, Hitchens remade himself as a zealous and strident supporter, in his writings and through public debates and his many appearances on American television, of the so-called war on terror, to the dismay of many on the left. In the arguments over dodgy dossiers and unilateral declarations of war, he sided with George W Bush, Richard Perle, Paul Wolfowitz and Tony Blair rather than with his old friends on The Nation.

He had, at last, found his grand anti-totalitarian cause. A robust Manichean, he denounced “Islamofascism”, a catch-all term that was so loose, generalised and opaque in its application as to be meaningless. The Taliban, Iranian Shia theocrats, Sunni al-Qaeda operatives, British Muslim jihadists, Hamas, Hizbollah – in spite of their different origins and distinct socio-political circumstances, they were all “Islamofascists”.

Hitchens believed his mission was comparable to that of Orwell and those who presciently warned of, and wrote against, the dangers of appeasing both communist and fascist totalitarianism in the 1930s. He became a hero to neoconservatives and the pro-war left, the leader of the pack: “The Hitch”, the journalist-as-brand-name. In 2004, he visited Afghanistan, on a well-funded assignment for Vanity Fair, and was rather delighted by what he discovered there, especially by what he called “the small victories of the profane over the sacred”. “I will venture a prediction,” he wrote. “The Taliban/al-Qaeda riffraff, as we know them, will never come back to power.”

It’s always unwise to make predictions, as any horseracing tipster or macro-economic forecaster must know, but Hitchens was wrong about the Taliban, with whom the western allies are now being forced to negotiate from a position of weakness, and the whole Afghanistan and Iraq misadventures. His general knowledge of the Middle East is superficial, he speaks no Islamic languages and, unlike, say, the politician-writer Rory Stewart or the Indian novelist Pankaj Mishra, he has made no serious, long-lasting attempt to immerse himself in the politics and cultures of this extraordinarily diverse and heterogeneous region, ravaged for so long by civil war and despotism, and destabilised by repeated foreign interventions.

In a long review of Koba the Dread, Hitchens writes that: “History is more of a tragedy than it is a morality tale.” Too often, when discussing the 10 years of war since 9/11, and in his chosen role of defender of “secularism and democracy”, Hitchens seems to have exchanged his tragic sense of history for the rhetoric of the western triumphalist.

How will Christopher Hitchens be remembered? In many ways the comparisons made between him and Orwell, to whom he returns again and again, as evangelical Christians return to Jesus (“What would George do?”), are false. Unlike Orwell, Hitchens has no one definitive book, no Animal Farm, Nineteen Eighty-Four or Homage to Catalonia. He is not a philosopher and has made no original contribution to intellectual thought. As an atheist, his anti-religious tract, God Is Not Great, is elegant but derivative. His polemical denunciations and pamphlets on powerful individuals, such as Mother Teresa, Bill Clinton, Ronald Reagan and Henry Kissinger, feel already dated, stranded in place and time, good journalism but not literature.

Ultimately, I suspect, he will be remembered more for his prodigious output and for his swaggering, rhetorical style – as well as for his lifestyle: the louche cosmopolitan and gadfly, the itinerant man of letters and indefatigable raconteur. The culture no longer throws up people like the Hitch. Today, he is very much a man apart. He has no equal in contemporary Anglo American letters; there are followers and disciples but no heir apparent.

AJ Liebling used to say that: “I can write better than anybody who can write faster, and I can write faster than anybody who can write better.” There are better writers than Hitchens, but none surely who can write as fast and as well as he does, and on any range of subjects. His confidence and overweening certainty can be tiresome and his political judgments are often foolish. He purports to loathe extremism and fanaticism, but in many ways he himself is by temperament an extremist, which is why he joined the International Socialists as a young man and remained a member for so long, and why, once he changed sides, he became such a bellicose supporter of the neoconservative project.

In retrospect, the fall of the Berlin Wall did not liberate Hitchens as a political writer, as Amis suggested: even after 1989, his polemicising continued to be compromised by Manicheanism. He merely substituted one all-encompassing world view for another: first the global proletarian struggle, and then the global struggle against “Islamofascism”. The most notable development in the period covered by this book was his emergence as a literary critic of distinction – and it is here that the sense of liberation that Amis identified in his friend is most palpable.

Above all, Hitchens has never lost his sense of humour. Or his sense of outrage, which, when controlled, as in his devastating 2006 account of the effects of Agent Orange on generations of Vietnamese, is his most potent weapon.