One might imagine that the duties and responsibilities of the office of first minister of Scotland would preclude much time for hinterland. But anyone who follows Nicola Sturgeon’s Saturday night Twitter feed, detailing her weekly reading, will be aware that this is a woman who devours books. Her recommendations may range from crime to rediscovered feminist classics, but her passion is clear and unconfected.

Reading, she explains, and fiction in particular, offers an escape from whatever anxieties are consuming her working days – as well as delivering a unique insight into other lives and circumstances that informs her political understanding in a way that no dry civil service briefing could.

So it should come as no surprise that Sturgeon was eager to have a conversation with the novelist Rachel Kushner, whose third novel, The Mars Room, the Scottish National party leader had read earlier this year. An immersive and often bleak portrayal of women’s incarceration in contemporary California, The Mars Room was shortlisted for this year’s Man Booker prize, following her much-praised second novel, The Flamethrowers, set in the 1970s Manhattan art scene.

Sturgeon and Kushner have been voracious readers since childhood, and both are acutely aware of the impact the habit of reading has on their professional and private lives. They first met this August, when Sturgeon hosted a PEN International event for the Edinburgh book festival at her official residence, Bute House; a photograph of the two women, which Sturgeon posted on Twitter, showed the first minister grinning with delight next to the novelist. Today, they meet again via Skype and, despite the distance and time difference – it is a bright morning in Los Angeles, a darkening winter afternoon in Glasgow – fall easily into conversation. Kushner sips a cup of tea while Sturgeon fiddles with a paperclip.

Nicola Sturgeon I know a lot of writers like to be anonymous and want their stories to be centre stage, but I’m always fascinated by what inspires you. I love literature that confronts challenging, important issues.

Rachel Kushner I wouldn’t exactly say it surprised me that a politician was interested in literature, because I’m half a century old and aware of world history – and traditions in countries unlike my own, where there have been leaders who were quite literate. But I was taken aback by it when we met; it seemed like a Valhalla to be there in your residence talking about books. The day before I’d been to visit a women’s prison, a place where I assume mainly working-class Scottish people end up. Then I was there talking to the first minister and she was as interested in the people in my book as I was interested in the women I’d met the day before.

NS Well, I hope so! My job, fundamentally, is all about people and it’s the individual stories that give me a sense of the issues I need to use my position to influence or change. That’s why I see reading fiction as an indispensable part of the job. I think all leaders in all positions of responsibility should be made to read fiction, because it uses personal stories to bring issues to life, and gives you a window that all of the academic reading or government civil service papers in the world doesn’t allow you.

RK It’s something I think about a lot myself: what is it fiction does that nonfiction and memoir don’t do? Maybe, in fiction, it’s no longer forming sentences from a deliberate place where the ego is firmly rooted. You’re having an encounter with your unconscious, and parts of life that don’t have to do with you, and you’re no longer in control of the narrative in the way that a nonfiction writer is. I don’t know if you agree.

Prison is invisible to a middle-class person. It’s a serious subject for a writer

NS Yeah, I do. I think the most important thing is to read, and I do read nonfiction and memoir. The last nonfiction book I read was Doris Kearns Goodwin on leadership. But I think with fiction, it’s the characters and the personal stories that come to the fore, so you’re seeing things from a very different perspective. And with the best will in the world, all memoir has a certain spin on it.

RK When I’m reading, I feel like a more wholesome person because I’m taking time to do something that is a practice. You learn to maintain concentration and have the opportunity to see, through somebody else’s attentiveness to detail in the world.

NS With fiction, I pay much more attention to style and form and sentence structure, and I think that makes you think a lot more deeply. You’ll be aware of the big debate in the wake of the Booker winner this year about difficulty in literature, which I find incredible! There’s no other art form where we’d see people having to think and be challenged by it as somehow a weakness. One of my own weaknesses as a reader, because I don’t have a lot of time, is that I tend to race through a book. The more I have to slow down and think about the structure of a sentence, the more I enjoy it.

I read The Mars Room, and I’ve since read your Cuba-based novel, Telex From Cuba. Do you write because there’s a subject that you’re passionate about, or do you develop an interest in the subject because you come up with a story idea first?

RK With The Mars Room, I wanted to write a contemporary novel [Kushner’s first two novels were set in 1950s Cuba and 1970s New York and Rome]. My immediate instinct for what is contemporary was what I see around me, as a person from California and a woman. This is a story that gets to the root of how my society is structured right now, and the way it’s going to intensify into populations that are going into the criminal justice system and reproducing themselves – and populations that aren’t and don’t, and can barely see that structure. There’s a way that prison is invisible to a middle-class person. It’s not a conspiracy, but it may be by design in certain regards. It’s a serious subject for a novelist.

NS Scotland is a much smaller country. We don’t have the sheer scale of the institutions that you write about, but there is the same sense of marginalisation and not seeing what is right there. Many of the people who end up in our prisons – and it will be the same in America – are already victims of other forces in society. Our prisons will be disproportionately populated by people who have suffered trauma and abuse in childhood, who have grown up in care. The prison system is often compounding the injustice they have suffered in their lives. It’s easy as a society to be aware of that on an intellectual level, but not focus on it.

One of the things I’m passionate about is trying as a society to reduce the circumstances in which people end up in prison. Obviously there will be some crimes where prison is the only – and the right – place to go. But we’re focused in Scotland on trying to look at other, more community-based sentences, where rehabilitation is at the heart from the outset; and, secondly, when people are sentenced to a term in prison, that we don’t lose focus on the rehabilitative element.

The impact The Mars Room had on me was that real sense of utter hopelessness. You have somebody given two consecutive life sentences with no possibility of parole – that sense that there is no hope, no redemption that somebody can hold on to, is incredibly bleak. I think when a prison system gets to that level, it is failing.

You visited a women’s prison when you were in Scotland. What was your impression, in terms of the similarities and, hopefully, the differences?

RK I was there for only part of a day, but just waiting to go through security, I had the opportunity to see all the people lined up for family visiting – and that was amazing, to see who was there. I thought, bourgeois societies are related the world over, because it is the poorest people who are subjected to this and who are bringing small children and newborn babies here, because they don’t have other care. Or maybe they are visiting people who want to see the children. In that way, it was similar.

But the people who took us into the prison were much more informal. There was no hostility towards me, and the Edinburgh book festival had found a benefactor to buy copies of my book for all the women who attended my reading. This would never happen in California! In fact, the California Department of Corrections does not want any books by donation. I’ve been trying for a year now to get their head librarian in Sacramento to accept a donation.

Reading your book reaffirmed what I believe – that prison, particularly for women, should be a last resort

There was a warmer contact between the women and the female guard who brought me in, who was there through my reading. She asked if she could speak at the end of the Q&A and offered her own feelings about her experience of women inside. And she started to cry. It was incredible, because that would never happen in the United States.

I have much empathy for people who work in the justice system. That is not an easy job. In California, studies have shown that people who work as guards in facilities have almost as high a rate of mental illness and suicide as veterans who come back from active combat. In order to get through that, they go in with a warlike mentality. To see this dialogue was something different.

What was similar was the trauma and the hardships these women had endured prior to whatever act they had committed that resulted in their incarceration, the same grain and texture. You can see it in people’s faces.

NS Reading your book had such an impact on me. I don’t think it changed my thinking, but it reaffirmed what I already strongly believed – that prison, particularly for women, and women with children, should be a last resort. Rehabilitation should be as important in the justice system as punishment is.

Facebook Twitter Pinterest ‘I would love to swap places!’ Photographs: Barry J Holmes and Murdo MacLeod for the Guardian Photograph: Barry J Holmes

That impacted on me as a leader all these thousands of miles away, but in America, is there any sense that literature can have that effect, can start to push change? In Scotland, and the UK generally, there is an openness to the debate about the role of prison and rehabilitation. Is there any sense in America that books like yours can nudge things along?

RK I think there are a lot of people who are open to dialogue. Art can allow someone to ask questions about what is justice, how does the law work, what is this axis of innocence versus guilt? And is it really relevant when you find that all the guilty are from one layer of the population, and is it really guilt if all those people have been exposed to enormous amounts of trauma and violence by the time they themselves act like that? The novel allows me to ruminate on things that have real moral complexity and no simple answers.

I think there is a wave now of people realising that prison isn’t the answer, but I still see a rudimentary fixation on guilt by people from the middle class. I think it’s deeply tempting for those people, who are the products of nurturing and opportunity and education, to feel their successes in life are a product of their goodness. It isn’t that those people are not good, but that they do not know how their lives would have gone if they had been born into an environment where they had to endure hardship and trauma and chaos and violence.

NS Yes. I think, as a politician, that should also be one of the most important things we focus on: why people end up there. All of us like to think our successes in life are down to our own brilliance and hard work, rather than the advantages we’ve had growing up. But the flipside is that, with people who commit crime, it’s easier to think that’s entirely down to the choices they have made – because then we don’t have to take our own collective responsibility for the societal circumstances in which they end up. I’m not trying to say there shouldn’t be an element of personal responsibility. But the reasons people end up in prison are complicated and often have their roots way back.

For a politician, this can be really challenging territory. Even in a relatively progressive society such as Scotland, I get challenged frequently in parliament about policies focusing on rehabilitation and trying to keep people out of prison; they get characterised as being soft on crime, when actually we all benefit as a society if we address the reasons why some people end up where they do.

I’m glad you’re a politician because you’re talented at it, clearly. I’m glad they have you in Scotland

RK That was all so beautifully put. I was thinking when we started to speak, I’m so glad I’m a novelist and not a politician.

NS I would love to swap places!

RK But I’m so glad you are a politician because you’re talented at it, clearly. I said it because the novelist can range deeply into the moral complexity without having to produce policy at the other end. But I’m glad they have you in Scotland to challenge people.

NS I was going to chance my arm and ask what you’re writing now…

RK Oh gosh, I have a new novel that I’m working on.

NS That’s what I like to hear.

RK It’s such a different subject and it might sound a bit wild. How to explain this: I’m quite taken with the new scientific discoveries about human migration patterns in Europe. When they sequenced the entire genome of the Neanderthal, it transformed our understanding of prehistory – and now geneticists think there was one homo sapiens walking north from Africa who encountered one Neanderthal in Europe. These people got together and this resulted in between 2% and 4% of Neanderthal DNA in Europeans. To me, it’s a love story!

NS This is the subject of your next novel? I can’t wait.

My last question to you is about the US midterm election results. Are you optimistic or pessimistic?

RK Oh gosh, I just don’t know. Part of that is, I was out of the country when they occurred, and I came home to Los Angeles, where we had a mass shooting and fire storms, and I think we’re trying to survive those and then see. But we have had some victories as progressives – so, careful optimism.

My last question is also a comment. It was a statement that you made about your biggest influence being Margaret Thatcher? [NS laughs] I found this so wonderful and I read it to my mother who burst out laughing, but maybe the same can almost be said of me. When Reagan was elected, he was in a way our Thatcher, and when he was elected I cried. I was a child but I understood that the other side had won. Thatcher and Reagan had this famed connection as ultraconservatives and there were huge protests in San Francisco in 1983, when Queen Elizabeth II dined with Reagan in Golden Gate Park, just a few blocks from my childhood apartment. They were directed at Reagan and Thatcher and their political alliance, and all that they each, and cumulatively, stood for.

NS I did say that. When Thatcher became prime minister, I was nine years old and I remember, through the 1980s, when her policies were doing such damage to the community I grew up in and working-class communities all across Scotland. It was my anger at that that really sparked my interest and shaped the politics I have today. So I probably owe it all to Margaret Thatcher!

But I like to think that across America right now, there’s a younger generation of future politicians and activists who are being inspired in the same way, by a certain incumbent of the White House.

RK And that should be our closing statement.

• This conversation appears in the Guardian’s Weekend magazine and has been edited and abridged for length.

If you would like a comment on this piece to be considered for inclusion on Weekend magazine’s letters page in print, please email weekend@theguardian.com, including your name and address (not for publication).