Chinese sci-fi is having a moment. Liu Cixin’s bestselling alien-invasion trilogy “The Three-Body Problem” has sold more than 4m copies. Since 2015 it has won international fans too, after becoming the first Chinese book to win the prestigious Hugo award for best science-fiction novel, and a major movie is due out this year. But whereas Liu, 53, writes about aliens, physics and man’s place among the stars – traditional science-fiction concerns – a new generation of Chinese writers is experimenting with the genre as a way to discuss the realities of 21st-century China.

Hao Jingfang won international acclaim when one of her stories, “Folding Beijing”, won the novella category in the latest Hugo awards. In China the story was hotly discussed online, not just for its literary merits, but also for its social criticism. The story follows Lao Dao, a migrant sewage worker living in the underbelly of the capital who is saving up to pay kindergarten fees for his adopted daughter. Yet this Beijing is divided into three segments: an elite 5m live in “First Space”, 25m more occupy “Second Space” and a teaming underclass of 50m are in “Third Space”, where Lao Dao toils.

As well as being separate socially, these strata are physically divorced. Every day at 6am the skyscrapers of one space fold in on themselves and pivot like “gigantic Rubik’s cubes” so that the earth literally turns over to reveal the next lot who have their turn at living above ground. Lao Dao rides the folding, morphing city up into Second and then First Space, smuggling a lover’s message and stumbling across an explanation of how the city came to be as it is.

As a commentary on inequality and those who are left behind by China’s breakneck urbanisation, Hao’s message is hard to miss. (Her inspiration for the story was a Beijing taxi-driver who complained to her about his daughter’s high kindergarten fees.) Over coffee in a central hutong near where she lives, Hao told me how her central theme was the “disease of big cities”, where “the rich never encounter the poor” and development leaves the underclasses behind. “I wanted to express my ideas about how isolated people are from each other,” she said. But chatter among Chinese readers focused on how the story handled migrant workers, stagnating social mobility and the super-rich who control the city. Even the authorities got nervous, closing down discussion threads online – an act worthy of its own dystopian sci-fi.

Now 32, Hao read “Fahrenheit 451” and “Around the World in 80 Days” in translation as a child, before getting into the sci-fi classics of Isaac Asimov and Arthur C. Clarke. At Tsinghua University in Beijing she read physics before switching to an economics P h D (both subjects helped her to “see the world as a big system”). Meanwhile, her own fledgling sci-fi was a “mental experiment” in how to consider the society around her.

Her first novel, “Wandering Sky” (as yet untranslated), depicts two worlds: an Earth dominated by a global market and an automated Utopia on Mars. To Hao the metaphor represents China’s generation gap, in which people like her, who were born in the 1980s, now occupy a different world to their parents. In another short story, “The Last Brave Man”, she explores the role of the individual in a collectivist society through the tale of a fugitive clone, Si Jie 47, who is being hunted by the authorities. And in “Invisible Planets” we are reminded of China’s noxious air pollution through the planet of Chincato, with an atmosphere “so dense that no light can penetrate it”.

Hao is not the only one to use the misdirection of the form to explore hard truths. Chen Qiufan, 35, uses his sci-fi stories to explore sensitive issues including smog and graduate unemployment. In “City of Silence”, by Ma Boyang, citizens communicate online using a list of “healthy words”. Authors in other countries have long used the genre to satirise or issue warnings, from “1984” by George Orwell to Yevgeny Zamyatin’s Soviet-era dystopia, “We”. Chinese science fiction has a history of veiled political commentary too: Lao She’s 1933 novel, “Cat Country”, for instance, depicts a Martian civilisation that is addicted to opiates and seeks liberation through a new ideology called “Everybody Shareskyism”.

Hidden meanings are even more precious in today’s China, where essays and realist literature are subject to strict censorship while sci-fi, often dismissed as kid’s fare, can slip more easily past the censors. China has gone through such monumental changes over the last few decades that the futuristic mode is a natural fit to express its complexities. When regular literature fails to directly tackle social or political issues – or is sanitised when it tries – it is no surprise that readers look to more imaginative fare. As Hao says, in sci-fi you can talk about things more freely. And in China, the truth is often stranger than science fiction.