The French poet and novelist Michel Houellebecq is not a nice man. Just look at him: pouting, prematurely aged, kippered by cigarette smoke. He writes about sociopathic middle-aged men who consume porn, hate women and indulge in sex tourism.

He has a reputation for being a little like the characters in his books, who are reactionary, racist, misogynistic. He was taken to court in France in 2002 for describing Islam as, among other things, “the dumbest religion”, but was found not guilty of inciting religious hatred.

When it emerged that Houellebecq was writing a book about France becoming an Islamic state in 2022, it was assumed that this would be a polemic against the spread of Islamic fundamentalism or a satire on religious conversion. It turns out to be neither – at least in my reading. It is a fascinating and disturbing vision of a society which becomes an accidental theocracy.

Submission is about a misanthropic, washed-up academic, Francois, who discovers a kind of inner peace when he reluctantly decides to become a Muslim. It is set against a background of a France which resolves its post-capitalist contradictions by becoming an Islamic state.

Francois's epiphany takes place shortly after the moderate-sounding Ben Abbes, leader of the Muslim Fraternity, succeeds in becoming President of France after an election in which Marine Le Pen's National Front come out top. The socialist and the centrist UMP parties decide that Abbes's programme is more humane than that of the far right – and so they support his bid to become President.

The Muslim leader – compared somewhat outrageously in the book to Charles de Gaulle – doesn't seek a hand-chopping Islamic revolution. On many economic and social issues he is rather leftish. The only government department Abbes wants to control is education, so that he can ensure that Islamic schools are set up based on sharia law and with strict sexual segregation.

These prove to be rather successful, and non-Muslims start sending their children there. Indeed, French society as a whole seems to be more at ease with itself under Muslim governance. The rioting banlieues are calmed. Crime falls dramatically in urban areas. Unemployment is eliminated as women are forced to give up work and raise children. Sex trafficking and prostitution are banned as men are allowed to take on extra wives. Abbes creates a plan for a pan-European Muslim EU under French leadership – a Francophone caliphate.

As the Islamic state gradually takes over, Francois loses his university post because he isn't a Muslim. He takes a road trip through rural France and decides that, since Islam is the only game in town, he might as well convert. His literary hero is the French 19th-century novelist Joris-Karl Huysmans, who was connected with the Decadent movement and who himself ended up converting to Catholicism.

Houellebecq's message here is pretty clear. French society is disintegrating under soulless capitalist materialism. Order needs to be restored. Only a return to religious certainty and patriarchy can save civilisation from moral permissiveness, class conflict and crime.

This is a classic novel of the reactionary right which has cleverly concealed itself behind a veil of multiculturalism. By making his religious renaissance Islamic rather than Christian one (Houellebecq has said that he originally intended his anti-hero to undergo Catholic conversion but changed his mind), the author kills several birds with one stone.

First of all he removes himself from the firing line. After having made derogatory statements about Islam, he must surely have worried that he might be on the terrorist hit list. This book came out in France contemporaneously with the Charlie Hebdo attacks, but Houellebecq can quite legitimately claim that his is a rather benign interpretation of a sharia regime.

Indeed, an Islamic state turns out to be a bit of a paradise on Earth so long as you aren't a woman, a scientist, an atheist or a Jew. Gulf states pour money into the French economy. Francois’s Jewish girlfriend, Myriam, has to leave as Jewish people take flight. But he's so raddled with dissipation and intellectual ennui that he seems indifferent to the loss and consoles himself with prostitutes and the thought of young Muslim brides.

Feminists aren't going to like Submission. And it isn't a great work of literature – the writing is a bit tired, like the characters, and the political twists are often contrived. There are rambling philosophical digressions and a juvenile preoccupation with pornographic detail. But you have to hand it to Houellebecq: the central idea of a western country turning to Islam, not through conquest but voluntarily and with the support of the political establishment, is a rather brilliant conceit, worthy of George Orwell. It is of course nonsense, but that doesn't matter. This is a novel, not a work of social science.

Houellebecq thinks Western liberals are just useful idiots being sympathetic to Muslim communities, despite Islam's attitude to women, abortion and homosexuality. I disagree. Such sympathy arises out of concern for a persecuted minority and on grounds of human rights, not because the left is susceptible to its religious doctrines. Nevertheless, it is not inconceivable that with mass immigration, a Muslim party could start seeking election in European democracies. And it is not beyond the bounds of possibility that they could enter into electoral arrangements with other parties. My own view is that they would be much more likely to form alliances with the political right than the left.

But the debate is worth having. Submission is a fascinating and original dystopia – challenging and ambiguous. It is a vision of what could happen if the West finally abandoned liberal enlightenment values and fell into the arms of religion. Houellebecq thinks it wouldn’t be all that bad. The rest of us can only hope it never comes to that.

Submission by Michel Houellebecq is published by Heinemann, £18.99