It has been 10 years since Eleanor Catton became, at 28, the youngest writer to be awarded the Booker prize. The Luminaries, a Victorian mystery set during the New Zealand gold rush, was the longest book to win in the prize’s history and made her only the second New Zealand writer to have done so, after Keri Hulme. Since then, she has adapted it for the BBC and written a screenplay for Emma (both of which aired in 2020), got married and had a baby. But it has taken her a long time to get back to fiction, she says, when I visit her at home in Cambridge, where she is living with her husband, the American poet Steven Toussaint, as he studies for a PhD in divinity and philosophy of religion at the university. “The Booker prize was life-changing, but it wasn’t self-changing,” she says. “Having a child is truly self-changing.” They have just returned from a trip to Auckland, her first visit home since the pandemic, and the first time her parents had met her two-year-old daughter. By coincidence, on the day we meet Jacinda Ardern announces she will be stepping down as prime minister of New Zealand. While Catton has been a fan, she says, she took the closing of her home country’s borders at the peak of the pandemic “kind of personally”. As Catton points out, when Ardern thanked her “team of five million” New Zealanders for the sacrifices they were making during lockdown, she failed to include all those who were stuck overseas, like Catton, who had just moved to the UK, “and who were also making an incredible sacrifice. They were a part of that team, but they weren’t honoured as such.” Catton, now 37, often begins her sentences with the phrase, “I’ve thought a lot about this recently”, and she really has. Feeling “rather disgruntled” made it easier to write her new novel, Birnam Wood, a satire-cum-psychological-eco-thriller about a young guerrilla gardening collective, set in a fictional New Zealand national park. Most of the novel was written during lockdown and pregnancy; she finished the final sprint while her daughter was still tiny. “Steve would knock on my study door with the baby. I would feed her and then I would hand her back and keep going.” Birnam Wood is Catton’s third novel. Her first, The Rehearsal, an ingeniously crafted story about teenage girls and a sex scandal in a New Zealand high school, was published in 2008 when she was only 22, and reviewers eagerly welcomed an original new talent. Then came The Luminaries, sending her into a different stratosphere overnight. Winning the Booker may sound like every young writer’s dream, but it was a profoundly alienating experience, she says. “I just felt so much doubt all of a sudden. My book was selling in this crazy way. It felt so disproportionate to my relationship to it.” Then she found herself at the centre of a media “firestorm” in 2015, after comments she made at the Jaipur literature festival about New Zealand politicians – “neoliberal, profit-obsessed, very shallow, very money-hungry” – were picked up back home. She was accused of being a traitor and an “ungrateful hua” (Māori slang for an unpleasant woman), with even the then prime minister John Key sniping on breakfast television that she didn’t know what she was talking about and should stay out of politics. “It was an extraordinary smackdown,” she says. Her parents were doorstepped. The whole experience was “relentless and frankly devastating”. After an older man glared at her in the supermarket and let out an exaggerated disapproving sigh one day, she went home and didn’t leave the house for six weeks. “It just ruined me,” she says. “It knocked the joy out of me for a really long time.” But the ordeal did lead her to finally write, and sell, a proposal for Birnam Wood in 2017. In response to Key’s jibe she immersed herself in history and political books, which “in a funny kind of way birthed the novel”. (She has the last laugh on Key, alluded to in the novel as the “moneyed politician” who reinstated chivalric titles in New Zealand before being knighted himself.) The novel revolves around the New Zealand national obsession: property. The young anti-establishment members of the Birnam Wood collective want to use Thorndike Farm to grow produce, and American billionaire Robert Lemoine wants to buy it, posing as a survivalist who plans to build a refuge there as a cover for an illegal rare-earth mining operation. Characters are broadly divided along generational lines – idealistic twentysomethings Mira and Shelley, gen X baddie Lemoine and benign but smug baby boomers Lord and Lady Darvish, who actually own the land. Birnam Wood addresses many of today’s hottest issues: the moral depredations of late capitalism, the dangers of rampant technology, surveillance, social media and environmental collapse, and the question of who is to blame for it all. While Catton shares her generation’s anger at the boomers – for presiding over a period that has seen the introduction of university tuition fees, the financial crisis and an acceleration of the climate crisis for starters – the novel’s sharpest satire is directed at her own tribe: well-meaning, left-leaning millennials. With its zeitgeisty subject matter, Birnam Wood couldn’t be more different from The Luminaries, which some critics dismissed as pastiche and “costume drama”. The novel was subjected to some rather sneery, sexist, and what Catton has called “bullying” reviews, especially in New Zealand, and particularly from “men over about 45”. But she was also compared to George Eliot and Wilkie Collins, and to experimentalists such as Italo Calvino. Both The Luminaries and Birnam Wood are driven by a human greed to plunder New Zealand’s natural resources. When Mira agrees to accept funding from Lemoine (unaware of his nefarious intentions, although his megabucks from drone manufacture might have set off alarms), Catton is making the point that in blaming the boomers we wilfully ignore other bad actors in the world. “Millennials are quite willing to cosy up to the tech gen Xers,” she says. “We are all personally enriching billionaires like Elon Musk by freely giving away our data.” Her mobile emits a timely buzz. “These minerals are in the phones that are around us all the time. I want my iPhone. I want to be able to have the freedoms that it brings. We are all complicit.” As with The Luminaries, she started her latest work with a title and a chart. Readers of that earlier novel will remember it was written according to a complex astrological schema, where each character corresponded to a zodiac sign, created with the help of a website that tracked the planetary movements over 19th-century New Zealand. “The Luminaries was so baroque, it’s almost camp,” she laughs. “There was an element that was play for the sake of play. It was me having fun, just seeing if I could do it.” With Birnam Wood she had a serious message. This time she looked not to the heavens but to the classics, with Shakespeare and Austen (and a little Lee Child) providing inspiration. From Macbeth she took not only the title (a wood of the same name plays a pivotal role in the Scottish king’s downfall), but drew up another intricate masterplan in which each of the main characters could be seen as Macbeth, with a corresponding Lady Macbeth, witches and so on. It sounds tricksier than it is: as the narrative perspective shifts, everybody could be the villain. She wanted to stop readers playing “the polarised blame game we are all used to in contemporary politics,” she explains. “You wouldn’t be able to say: ‘These are my people so they are obviously the good guys. These are the people that I despise so they are obviously the bad guys.’” But it was working on the screenplay for Emma, which she had never read before (though she had seen the loose 90s adaptation Clueless), that finally impelled her to start writing in earnest in 2019. Collaborating creatively with other people was a relief from the “intellectual loneliness” she felt after the Booker. Like another Booker winner, Damon Galgut, she says she would recommend a screenwriting sabbatical to any novelist struggling with writer’s block. “I didn’t want to write a book where nothing happened,” she says. “Where the book participated in any sort of apathy or nihilism by just kind of shrugging its shoulders and saying: ‘Well, actually, nothing is going to change, the writing is on the wall already.’ I wanted the book to show that actions do matter.” And it wasn’t just about creating a pacy plot (although the ending will have you gnawing your knuckles). “It seems to me that morality has always depended on there being a difference between saying something and doing it: saying I am a good person and then doing a good action,” she says. This distinction, she believes, has been eroded in our digital world, where you are what you tweet. Five years ago she quit all social media and hasn’t looked back. “I think that it is distorting human nature,” she says. “It’s altering the way that we think. It’s altering the way that we exist in time.” She compares tweeting to “throwing a paper dart into the void” with no idea who that dart will hit or any obligation to follow up. “There’s no engagement with all of the more human emotional considerations that would come into an actual debate. It’s no wonder that these things become so poisonous and so polarised and so insoluble.” In a set piece in the middle of the novel – by far the hardest part to write, she says – two Birnam Wood members have an argument that descends into ranting and mansplaining on one side and self-righteous sensitivity on the other: “‘Um, just so I’m clear,’ Amber said, ‘you’re saying that intersectionality is bullshit?’” Catton wanted to satirise the toxicity of so much public discourse, particularly on the left, which she feels has become “a kind of purity test” in which you are judged on using the right language or not. “‘Is a woman a woman?’ for example. It becomes this kind of test.” Researching psychological traits for her James Bond-esque villain Lemoine, she was struck by the similarities between our relationship to the internet and that of sociopaths to their victims. “Algorithms are flattering you by adapting themselves to what they think that you want; they can see what you desire and they’re very good at shapeshifting,” she says. “We’ve kind of become acclimatised to dealing with sociopaths, through our constant engagement with algorithms. It’s not an accident that there are so many sociopaths in positions of power.” Catton has always had a “slightly outsider perspective” on New Zealand culture, a result, she believes, of having been born in Canada with an American father. The family – she is the youngest of three children – moved to Christchurch when she was small. Her father was a philosophy lecturer at the university, her mother a librarian. They didn’t have a television – her parents still don’t. “There was a very strong, almost moral, pressure that books were better,” she says, and the young Eleanor would sit for hours wrapped in blankets writing stories on the computer in the garage. Clearly, having wrestled her giant novel into a miniseries, Catton is a TV convert, and cites hit shows such as The Wire and The Sopranos as an influence on The Luminaries (one of the Booker judges described it as “a Kiwi Twin Peaks”). Her daughter is giggling at a cartoon in the other room as we speak. She met Toussaint when they were both studying at the world-renowned Iowa Writers’ Workshop, for which she won a New Zealand scholarship in 2008, and where she would later teach. She had already published The Rehearsal and was at work on what would become The Luminaries. Together, the couple moved to Auckland in 2011. To call him her first reader, she says, would be to hugely underestimate the role he plays in her writing. They have “endless conversations”, sometimes – as with the dramatic ending of Birnam Wood – to the point of tearful arguments. “We are very explosive about it.” Although the UK now feels like home, she can’t resist returning to New Zealand in her fiction. Unlike so many writers, she is happy to talk about her next work, “a queasy immersion thriller” that will be called Doubtful Sound, after the remote fjord in the south-west of New Zealand where it is set. She has had the title for a long time – “I just think it is so beautiful” – but it was only in the final months of completing Birnam Wood that the story came to her. A mysterious box has been delivered while we are talking. It turns out to be finished copies of Birnam Wood from Catton’s publisher. The black and white jacket includes an endorsement from Stephen King that only came in at the last minute. “It’s as good as it gets,” King says of Catton’s third book. An author would be forgiven for posting a photo on Twitter. But after all this time, Catton is happy to just share the moment with her husband and daughter. Birnam Wood is published by Granta in March. To support The Guardian and Observer, order your copy at guardianbookshop.com. Delivery charges may apply.