Ali Smith’s door is ajar. She lives in Cambridge, on a half-hidden terrace of tiny Victorian cottages. The gardens are opposite, the fences between them long since removed. It’s late September, and Smith’s beloved apple tree is still swagged with fruit. Inside, a green sweater slung over her shoulders, she beckons me upstairs to her studio to catch the last of the sun.

She’s only just finished her new novel, Autumn, the first in a shape-shifting seasonal quartet about time and history, art and love and the state the state is in. Its now is right now: turbulent Brexit Britain, where people scan the papers on their phones “to catch up on the usual huge changes there’ve been in the last half hour”.

Maybe an accelerated news cycle requires accelerated art. A manuscript usually takes a good year to be birthed into the world as a book, but Autumn sped through the presses in a matter of weeks. I can’t remember reading a novel that felt so firmly footed in the present. The stabbing of MP Jo Cox, children’s bodies washing on to beaches: all the nightmarish news of this summer has filtered into a narrative Smith initially planned as a farce about an antique shop.

How can we live in the world and not put our hand across a divide? How can we live with ourselves?

“All across the country,” she writes of the referendum, riffing on A Tale of Two Cities, “people felt it was the wrong thing. All across the country, people felt it was the right thing. All across the country, people felt they’d really lost. All across the country, people felt they’d really won… All across the country, people felt history at their shoulder. All across the country, people felt history meant nothing.”

But for all its immediacy, Autumn also sets the congested present in perspective. Everywhere there are unlikely friendships and enriching, practically Socratic dialogues. People fall in love and conduct bedside vigils. A painter is rediscovered. A young woman in 1940s France refuses internment. Time turns tricks; time flies; a man flings a watch into a canal. The cumulative effect is liberatory, expansive, like stepping out of a fetid room and finding yourself in a field.

I can’t pretend total objectivity here. I’ve known Smith since I was 17 (her partner, the artist and film-maker Sarah Wood, is my cousin). In the 1990s we used to write each other letters. Recently I unearthed a blurry photograph she sent me 20 years ago of a cat’s tail dangling over a sofa. “I have a long-term plan to write a novella for each season,” she’d written on the back. “It seems to me the seasons are so gifted to us that it’s a kind of duty, a very nice one.”

Though she jokes now that she sounds like Katherine Mansfield pretending to be charming, this talk of gifts and duties gets to something essential about Smith. She believes in unselfish communal values such as altruism and generosity and has an infectious faith in hospitality, be it to new ideas or strangers. In addition to writing eight novels and five collections of short stories, she has fought against the mass closure of public libraries (“libraries matter because we’re living in an age of disinformation”) and the proposed scrapping of the Human Rights Act; is a patron of the charity Refugee Tales and a staunch advocate for young writers and writers who have fallen out of fashion. She’s not, in short, an artist who seeks to wall herself off from the world.

Listening to the radio in the run-up to the referendum, she was appalled by the collapse of dialogue, the creep of lies, the resurgence of a kind of bullying language – “go home”; “we’re coming after you” – she hadn’t heard since she was a schoolgirl back in the 1970s. “Human beings need to take in all the possibilities of rhetoric, all the varieties and versatilities and here was coming a loggerhead,” she says now.

“The notion of a referendum is in any case a divisory line: you choose one side. Meanwhile, you’ve got the mass division of 65 million people crossing the world from parts of it which are untenable, unliveable and in flames. And what’s left of the world deciding whether or not to open the gates or the walls or to build more gates or walls. How can we live in the world and not put our hand across a divide? How can we live with ourselves? It isn’t either/or. It’s and/and/and. That’s what life is.”

The time itself is tearing itself apart because a massive lie has dissolved itself through the country

The and/and/and of life is what her fiction is so artful at revealing. It’s hard to think of another contemporary writer so adept at splicing the ordinary and the marvellous, cracking open possibilities for exuberant invention and transformation in spaces as dismally quotidian as a care home reception or Post Office queue. Words migrate and morph; perspectives slip and skew; things change. “Language is like poppies,” a character observes in Autumn. “It just takes something to churn the earth round them up, and when it does up come the sleeping words, bright red, fresh, blowing about.”

Smith’s previous novel, the wonderfully double-jointed How to Be Both (which was shortlisted for the 2014 Man Booker, and won the Baileys prize for women’s fiction, the Goldsmiths prize and the Costa novel award), imagined a possible life for a real artist, the Italian Renaissance painter Francesco del Cossa, whose irrepressibly lively frescoes in the city of Ferrara have withstood earthquakes and wars. She’s fascinated by the stubbornness of art, its capacity to outlive its creator, to “float”.

British pop artist Pauline Boty, photographed at home in 1963. Photograph: Tony Evans/ Getty Images

Autumn is likewise concerned with an artist whose work survives despite long odds. Pauline Boty, nicknamed the Wimbledon Bardot, was a heart-stoppingly gorgeous proto-feminist pop-art pioneer. She painted the sexy, violent world around her with a sly, wry eye. In a surviving photograph, she lounges naked with an armful of roses against her own painting of Jean-Paul Belmondo, an oozy vaginal flower crowning his hat. (“I’m an intelligent nakedness,” Smith has her say. “An intellectual body. I’m a bodily intelligence. Art’s full of nudes and I’m a thinking, choosing nude.”)

Witty, clever and electrifying, Boty was at the centre of swinging London: dancing on Ready, Steady, Go!, making a luminous cameo as a love interest in Alfie. In 1965, she became pregnant and was diagnosed with cancer during a routine examination. She refused chemotherapy, worried it would harm the foetus, and died at the age of 28, a few months after the birth of her daughter. With that, she sank from history until, decades later, some of her radiant, riotous canvases were rediscovered, mildewed and covered in cobwebs, in an outhouse on her brother’s farm.

Smith was knocked for six when she first saw one. “There are people who stand for their times and oh my God, Boty stands for her time.” Her interest quickened when she discovered Boty had been commissioned by an unknown person to paint Christine Keeler, the model at the heart of the Profumo affair (the painting, Scandal ‘63, which can be seen in several photographs, has been missing ever since).

Autumn interleaves the schisms of 2016 with the trial of 1963. Both are key years, Smith thinks, in which a lie in the political sphere had dramatic consequences for society at large. Like Brexit, like the invasion of Iraq, the Profumo affair marked a turning point. “Meanwhile, the time itself is tearing itself apart because there has been a massive lie and the lie has come from parliament and dissolved itself right the way through the country and things change. It’s a pivotal moment. We were dealing with a kind of mass culture of lies. And it’s a question of what happens culturally when something is built on a lie.”

One of the things she loves about Boty’s playful, probing work is that it looks at how governing cultural myths are formed and perpetuated by way of images. She didn’t paint people so much as pictures of people already in wide circulation: Marilyn Monroe tottering in furs; the Beatles, Elvis, JFK being shot in the motorcade in Dallas. Like fiction itself, Smith thinks, “it reminds you to read the world as a construct. And if you can read the world as a construct, you can ask questions of the construct and you can suggest ways to change the construct. You understand that things aren’t fixed.”

BUM, 1966 by Pauline Boty. Photograph: Pallant House Gallery

On the wall above Smith’s desk is a porcelain branch breaking into leaf, surrounded by dozens of pictures. There are lots of Boty, with her panda eyes and swishing corn-coloured hair, alongside reproductions of her paintings. One of Smith’s favourites is of a woman’s spectacularly shapely arse, framed by a proscenium arch. Underneath, in huge red letters, Boty has painted the word BUM.

The light is fading. Downstairs, Smith brings us a plate of apples from her tree and two clasp knives. There are great piles of books and records everywhere, paintings propped casually on stacks of art magazines and proofs: an iceberg, a bowl of lemons, a watercolour of a pink lily against a wash of dense black. The lily is by John Berger, another writer dogged in his faith in art as a force for forging connections, illuminating and resisting what Shakespeare’s Thomas More calls “mountainish inhumanity”.

Where do we end up if we wall ourselves in, Smith wonders. Insist on fortifications, and you create a kind of prison for yourself. In Autumn an electric fence appears around a plot of common land, patrolled by the fictive security agency SA4A. It’s such an ugly, absurd spectacle: “Prison for trees. Prison for gorse, for flies, for cabbage whites, for small blues. Oystercatcher detention centre.” Far better to yank them down, to learn how to communicate in a different tongue, to welcome the stranger as a friend.

She knows something of what’s coming next in the quartet, if not what material the future will fling her way. Winter, she thinks, is a place where you can see really clearly, while summer is the luscious moment when the light kicks in and the leaves are fully spread. But ask about individual characters and she clams up. I’m particularly keen on Autumn’s puckish songwriter Daniel Gluck: a limber 101, his life spanning the sweep of a century. Many of Smith’s most memorable characters have been disrupters, from Like’s Ash and The Accidental’s Amber to Miles, the stubborn bedroom squatter of There But for The. Daniel, on the other hand, is a repairer: a good person, who makes being good seem sexy, elegant and fun.

In one of the novel’s most memorable scenes, he plays a storytelling game, with Elisabeth Demand, the precocious, unhappy girl who lives next door. When she insists on a character who wants war, he conjures up a killing field of pantomime characters, from Aladdin to Cinderella, “a surrealist vision of hell”. And then he lets time get to work on them, grass growing through ribs and eyeholes, costumes nibbled away, until there’s nothing left but bones in flower. I don’t want to give away the exchange that follows, but I found it at once more stringent and more consoling than anything I’ve read this year.

Fiction can do that: can make a space for reflecting, for generating novel ways of responding and reacting to lies and guns and walls alike. The mere act of cracking open a book, Smith thinks, is creative in itself, capable of inculcating kindness and agility in the reader. “Art is one of the prime ways we have of opening ourselves and going beyond ourselves. That’s what art is, it’s the product of the human being in the world and imagination, all coming together. The irrepressibility of the life in the works, regardless of the times, the histories, the life stories, it’s like being given the world, its darks and lights. At which point we can go about the darks and lights with our imagination energised.”