It is said that Jean-Paul Sartre turned white-faced with excitement when a colleague arrived hotfoot from Germany with the news that one could make philosophy out of the ashtray. In these two new books, Slavoj Žižek philosophises in much the same spirit about sex, swearing, decaffeinated coffee, vampires, Henry Kissinger, The Sound of Music, the Muslim Brotherhood, the South Korean suicide rate and a good deal more. If there seems no end to his intellectual promiscuity, it is because he suffers from a rare affliction known as being interested in everything. In Britain, philosophers tend to divide between academics who write for each other and meaning-of-life merchants who beam their reflections at the general public. Part of Žižek’s secret is that he is both at once: a formidably erudite scholar well-versed in Kant and Heidegger who also has a consuming passion for the everyday. He is equally at home with Hegel and Hitchcock, the Fall from Eden and the fall of Mubarak. If he knows about Wagner and Schoenberg, he is also an avid consumer of vampire movies and detective fiction. A lot of his readers have learned to understand Freud or Nietzsche by viewing them through the lens of Jaws or Mary Poppins.

Academic philosophers can be obscure, whereas popularisers aim to be clear. With his urge to dismantle oppositions, Žižek has it both ways here. If some of his ideas can be hard to digest, his style is a model of lucidity. Absolute Recoil is full of intractable stuff, but Trouble in Paradise reports on the political situation in Egypt, China, Korea, Ukraine and the world in general in a crisp, well-crafted prose that any newspaper should be proud to publish. Not that, given Žižek’s provocatively political opinions, many of them would. He sees the world as divided between liberal capitalism and fundamentalism – in other words, between those who believe too little and those who believe too much. Instead of taking sides, however, he stresses the secret complicity between the two camps. Fundamentalism is the ugly creed of those who feel washed up and humiliated by a west that has too often ridden roughshod over their interests. One lesson of the Egyptian revolt, Žižek argues in Trouble in Paradise, is that if moderate liberal forces continue to ignore the radical left, “they will generate an unsurmountable fundamentalist wave”. Toppling tyrants, which all good liberals applaud, is simply a prelude to the hard work of radical social transformation, without which fundamentalism will return. In a world everywhere under the heel of capital, only radical politics can retrieve what is worth saving in the liberal legacy. It is no wonder that Žižek is as unpopular with Channel 4 as he is on Wall Street.

In any case, market freedom and religious fundamentalism are far from mutually exclusive. “Spiritual” values have been enlisted by Asian nations for capitalist ends. The easy opposition between liberal permissiveness and fundamentalist repression must be rethought. The rise of Islamo-fascism, Žižek points out, went hand in hand with the disappearance of the secular left in Muslim countries, a disappearance the west itself did much to promote. Who now recalls that, 40 years ago, Afghanistan was a strong secular state with a powerful Communist party which took power there independently of the Soviet Union? Every emergence of fascism, Walter Benjamin wrote, bears witness to a failed revolution. In the Muslim world, the west has played a major role in stamping on such movements, creating a political vacuum into which fundamentalism was then able to move. It cannot now feign innocence of its predatory past in the face of the Islamist backlash it has helped to unleash. Those who are reluctant to criticise liberal democracy, Žižek suggests, should also keep quiet about fundamentalism.

Stentorian, faintly manic and almost impossible to shut up, Žižek is a man who gets out of bed talking about psychoanalysis and steps back into it holding forth on Zionism. As a frenetic intellectual activist, he always seems to be in six places on the planet at once, like Socrates on steroids. His day may begin with a visit to Julian Assange in the Ecuadorian embassy and end with writing supportive letters to one of the imprisoned Pussy Riot performers. In between, he passes his time antagonising a sizeable chunk of the world’s population. If he is a scourge of neo-capitalism, he is also a sworn foe of liberal pluralism and political correctness. He tells the story of how at an impeccably enlightened US seminar he attended, the chairperson began by asking each participant to state their name along with their sexual preference. Žižek throttled back the urge to announce that he enjoyed bedding young boys and drinking their blood. He also points out how much less forthcoming the participants would have been if asked to state their salaries.

All this may be because he comes from Slovenia. Small nations tend to have a perverse relation to more powerful ones, as anyone acquainted with the Irish can attest. There is a dash of the Dubliner Oscar Wilde in Žižek, a man who couldn’t hear a pious English sentiment without feeling an irresistible itch to reverse its terms, rip it inside out or stand it on its head. Žižek, who has the grim appearance of a hired assassin in a Jacobean tragedy, lacks Wilde’s stylishness and elegance. He also lacks his distinctive brand of humour. Žižek is funny but not witty. He tells some excellent jokes and has a well-honed sense of the absurd, but one couldn’t extract a book of epigrams from his writing, as one can from Wilde’s. Both men, however, are natural-born debunkers and deconstructors, allergic to high moral tones and good clean fun. That Žižek should be a skilled exponent of Jewish black humour, the Woody Allen of Ljubljana, comes as no surprise. Even so, his urge to deface and deflate is a long way from cynicism. Remarkably, he combines the tragic vision of Freud with a Marxist faith in the future.

Like the rest of his work, these two latest volumes are postmodern in form but anti-postmodern in content. Žižek has the eclecticism of the postmodern, along with its mixing of high and low genres. His books are broken-backed affairs which leap erratically from topic to topic. Absolute Recoil, which lurches from ideas of hysteria, art and absolute knowledge to God, death and the Fall, is grandly subtitled “Towards a New Foundation of Dialectical Materialism”, but this is a barefaced deception. There are only a handful of references to dialectical materialism in its 400 pages. Žižek’s books and chapters are rarely about what they say they are about, since he can’t help saying 50 things at once. He is postmodern, too, in his suspicion of originality. A good deal of what he says has been said before, not by others but by himself. He is one of the great self-plagiarisers of our time, constantly thieving stuff from his own publications. Whole chunks of Absolute Recoil reappear in Trouble in Paradise, and whole chunks of Trouble in Paradise appear twice over. He has now told the same jokes, recycled the same insights and recounted the same anecdotes dozens of times over.

Another postmodern aspect of his work is its merging of illusion and reality. For Žižek’s mentor Jacques Lacan, nobody is more self-deceived than the cynic who claims to have seen through it all, ignorant of the Freudian claim that illusion (or fantasy) is built into reality itself. The same applies to Žižek’s own writing. Are his books genuine arguments or public performances? How sincere is he intending to be? If he can be breathtakingly perceptive, he can also be outrageously irresponsible. Can he really be serious when he claims in Trouble in Paradise that “the worst of Stalinism (is better) than the best of the liberal-capitalist welfare state”, or is he just out to scandalise the suburbs? Does he really think that the sexual misconduct Assange is accused of is “minor”? Or take the fact that he has repeatedly argued for the radical potential of Christianity, and does so again in Absolute Recoil, despite the fact that he is a self-proclaimed atheist. It isn’t quite a question, however, of being a Christian in appearance but an unbeliever in reality. Instead, one might claim that he believes and disbelieves in Christianity at the same time. Or what if he thinks he is an atheist but actually isn’t? What if the God he doesn’t believe in knows he is a believer?

Žižek himself is a curious mixture of illusion and reality. In Trouble in Paradise, he speaks of Hamlet as a clown, and he himself is both intellectual and jester. Shakespeare’s jesters are conscious of their own unreality, and Žižek seems to be, too. As a man for whom the adjective “colourful” could have been specially invented, he is a cult figure who sends up his own cult status, a man in deadly earnest who is also an accomplished self-parodist. There is something fictional, larger-than-life, about his constant globe-trotting and flamboyant antics, as though he has strayed out of a David Lodge novel. His gargantuan appetite for ideas is admirable but also faintly alarming. One would not be altogether surprised to hear that he was put together by a committee and consumer-tested on various student focus groups.

When it comes to content, however, nothing could be further from postmodern pluralism than Žižek’s uncompromising revolutionary politics. It is a strange sign of the times that perhaps the most popular intellectual in the world is a dedicated communist. The lesson of Trouble in Paradise, subtitled From the End of History to the End of Capitalism, is plain: “a new Dark Age is looming, with ethnic and religious passions exploding, and Enlightenment values receding”. Žižek’s style is notable for its hardboiled refusal to be emotionally intense, another postmodern feature; but even he can scarcely contain his disgust at the vision of thieving bankers being subsidised by their ruined victims. As Bertolt Brecht inquired: what’s robbing a bank compared to founding one?

Trouble in Paradise, with its unerring ear for political cant, is a book that everyone, not least the Masters of the Universe, would profit from reading. Absolute Recoil, with its intricate reflections on materialism and dialectics, is likely to have fewer takers. There is less on cant and more on Kant. Even so, it contains some fascinating stuff on Kabbala, slave narratives, espionage, atonal music and God as the supreme criminal. No doubt we shall have a chance to read some of this again in his next few books.

• To order Trouble in Paradise: From the End of History to the End of Capitalism for £14.44 (RRP £16.99) and Absolute Recoil: Towards a New Foundation of Dialectical Materialism for £17 (RRP £20) go to bookshop.theguardian.com or call 0330 333 6846.

Terry Eagleton’s most recent book is Culture and the Death of God