This tale of neighbouring planets occupied by anarchists and capitalists reminds us that the old left has plenty to teach us, as the new right accrues ever more power

The government contains only the sneering rich and serves only the sneering rich. They loathe the poor and have ensured they cannot escape poverty and receive only the minimum of education and state support. The health service has been destroyed and those who cannot afford private care are crammed into ancient filthy hospitals where they go simply to die. Any protests are put down with brutal force. No, I'm not talking about the next few years of Cameron and Clegg's reign of terror. I'm not even talking about the future as envisaged by the Tea Party. I'm talking about Ursula K Le Guin's 1975 Hugo award winner, The Dispossessed, and her vivid descriptions of the dystopian world of Urras.

The inequality on Urras has naturally provoked a great deal of anger. 150-odd years before the story opens there was a huge revolution – but instead of taking the more usual step of hanging their oppressors from lampposts, a large number of the revolutionaries fled to set up their own ideal society. Close to Urras (I know! It's the funniest planet name since Uranus) there's an almost inhabitable desert world called Annares where the idealists set up an anarchistic society based on principles of shared wealth, shared responsibility and shared bedrooms. Superficially, the society works. Incredibly, the people on Annares don't even mind sleeping in dorms. But at the time the book opens, things have calcified. The revolution is no longer moving forward. New ideas are frowned on and feared, while greedy, self-interested people (derided as "propertarians" in the language the inhabitants have invented for themselves) have started to hog power. Discontent is brewing.

Chief among these rebels against the rebellion is a brilliant young physicist called Shevek, whom we first meet him as he is escorted to a transport ship that will take him from Annares to Uras. The chapters then alternates in an A-B, A-B pattern, the first strand providing a linear account of Shevek's coming of age and growing disillusionment with the anarchists of Annares, the second an account of his growing disillusionment with the Tories on Uras. (Like everything else in the book, this structure serves a serious purpose, since Shevek's big physics breakthrough is called the "theory of simultaneity" and plays around with ideas of time, beginnings and endings and the past happening at the same time as the present – just as the chapters do.)

On Annares, we learn that the establishment doesn't like his theory because it promises to provide a method of instantaneous communication that will disrupt their glorious isolation. We gradually come to realise, meanwhile, that the apparently intellectually free inhabitants of Urras just want to get their hands on Shevek's formulas so they can use them to crush all the other planets in the solar system. All of which leaves the poor fellow with a series of serious moral quandaries that Le Guin investigates with characteristic rigour and compassion.

Shevek's journey has a pleasing circularity and the route he takes is generally intriguing. Ideas burst from the page. Annares has been described as an ideal vision of a 1970s hippy commune, and there's definitely a hint of yoghurt-weaving worthiness to it – but it remains an impressive thought-experiment. There's some quality intellectual red meat in Le Guin's portrayal of how, given the right conditions, an anarchist society might function and malfunction. All the related insights into the nature of freedom, free will, community, wealth and power are equally worth chewing over. Meanwhile, the language used on Annares is particularly interesting. Its vocabulary is strangely limited. There often aren't words to explain – say – capitalist notions of ownership or to allow for a good satisfying bout of cursing. So such things seem very alien to the locals. This is a surprisingly successful fictional representation of the Sapir Whorf hypothesis (the idea that languages shape thinking and culture) and the fact that Le Guin makes it work is a credit to her talent.

On the subject of the latter, as anyone who has read a Le Guin book might expect, her prose is generally impressive. True (and this also should be expected) the writing can be dense, opaque and occasionally absurd; she doesn't exactly have a light touch. But there are some fine descriptions of desert life on Annares, and the struggle for survival, horrors and sensual joys available on Uras. There's also real emotional heft in Shevek's intellectual travails and a slow-burning love story.

But Shevek is also the book's great weakness. He is often a humourless bore who brings out the worst in Le Guin's writing: "His gentleness was uncompromising; because he would not compete for dominance he was indomitable." Music for him is an "urgent need". He doesn't drink beer and with his friends he talks earnest politics, mind-melting physics and extreme metaphysics. In short, he doesn't seem entirely real. Nor for that matter, does Uras, where the two extremes of the dissipated rich and worthy poor are painted with such broad strokes that the painting never quite coalesces.

Even so, this remains a challenging and urgent book. And, what's more, a good reminder that the old left has plenty to teach us, even as the new right accrues ever more power.

Next time: The Forever War by Joe Haldeman – aren't the Hugos great?