Sue Brierley does not want to talk about Nicole Kidman.

“What was it like to have Nicole Kidman play [me]?” she poses, at the start of our interview, before adding, with a firm laugh: “I’m a bit over that one so please don’t ask me!”

In 2012, Brierley was catapulted into the limelight when her adopted son Saroo found his long-lost birth mother in India using Google Earth. He had been separated from her when, aged five, he accidentally boarded a train to a different city. His rare feel-good reunion story was relayed in his autobiography A Long Way Home and the Oscar-nominated movie Lion.

Now Brierley has her own book out. Lioness tracks her traumatic, poverty-stricken childhood in rural Tasmania; her decision to adopt two boys from India; and, of course, her relationship with Kidman, who portrayed her with such heart in Lion and has two adopted children of her own. Softening somewhat, Brierley concedes: “It was a lovely experience meeting her and we have contact now and again. But it’s the big picture that has a lot more to offer.”

That big picture – a deep dive into families, domestic abuse, adoption, the “mother myth” and much more – is, in many ways, more fascinating than the oft-covered glitz and glamour of Hollywood. Written in straightforward, unembellished prose, which mirrors the way that Brierley – a sensible, kind, no-nonsense type – speaks, I could not put it down.

Brierley, 66, grew up in 1950s and 60s Australia with a downtrodden Catholic mother and a violent, unpredictable father. Struggling to make ends meet following her father’s often mad dash plans to make cash, they lived off produce from their vegetable garden, eggs from their chickens, and milk and butter from their two Jersey cows.

Children were, as Brierley writes, “incidental – they just happened along and their purpose was to work hard and support the family”. She was put to labour from a young age, “cranking a stiff handle to separate the cream from the milk and then winding the heavy handle of the churn to make butter … a thankless and repetitive task”. At home, she often bore witness to her father’s brutal beatings of her mother.

The trauma left Brierley a meek, withdrawn child. It also informed her views about parenting: in Lioness, while she refers to her mother as “Mum”, her father is called “Joe”.

The decision was not conscious. “I never really thought about why I was doing that. That term ‘Dad’ just wasn’t true,” she tells Guardian Australia. “And I do think to be called Mum and Dad should be an honour: it should be earned and it should be deserved.”

Her childhood left Brierley certain of two things: that she wanted to marry a loving, gentle man (a goal she fulfilled thanks to her husband John); and that she wanted to adopt children, both to give them a new chance in life and because she regards parenting as a privilege, not a right.

“I do not believe that everyone has a right to be a parent and I weep for those children who have parents incapable of fulfilling their emotional and physical needs,” she says.

Yet, in 1970s and 80s Australia adoption was no easy task: the authorities were unsympathetic to a couple who had no fertility issues and deemed them ineligible. In 1987, after changes to adoption laws and 16 years of waiting, John and Brierley welcomed six-year-old Saroo into their lives.

To qualify, they underwent medical, psychological and financial examinations. “I often wonder what would happen if all prospective biological mothers and fathers had to comply with this level of scrutiny and investigation before they were allowed to become parents,” writes Brierley. “I have a feeling many would fail dismally.”

Society, too, fails parents, Brierley believes. In particular, our enduring infatuation with the “mother myth”: “We have got an obsession about birth mothers being the only true mothers. But there’s a huge variety in the way women mother.”

Brierley says that adulation of birth mothers – born from the worship of the Virgin Mary as the ideal mother figure – has proved destructive for women, particularly those who can’t conceive. “There’s this sense of failure – you’re less than,” she says. “It creates a glorified image of [birth mothers] being the best and only way. I saw that kind of manipulation and pressure in my own life, in my Catholic faith, in my mother’s Catholic faith, in her mother’s. I really see myself as a recovered Catholic.”

And yet Brierley’s own belief in herself as a mother was challenged by difficulties she faced with her second adopted son, Mantosh. Following abuse in an Indian institution, he arrived in Australia aged nine in distress, and often lashed out at Brierley, sometimes physically.

“It destroyed my confidence in my parenting skills,” she admits. “I feared that it would end up being my father all over again.”

Mantosh, now 38, wept when reading the book, understanding, perhaps for the first time, Brierley’s own hardships. “There were things I wasn’t going to tell him [growing up] – he needed stability, he needed my strength,” she says.

The road for Saroo, too, has been arduous, despite Lion’s fairytale ending. He has purchased his birth mother Fatima’s house, providing her with long sought-after stability, and they talk on the phone through a translator. “Of course their relationship will never be fully recovered. There’s too much time and difference in living,” says Brierley.

Brierley, who had her own tearful meeting with Fatima in India, prefers to stay out of the way, leaving Saroo to develop his newfound, and sometimes tricky, relationship with his other mother unhindered. “We made our peace and I gave her my gratitude and it’s important that she [now] live her life.”

Lionness ends on a prayer: that Mantosh, too, finds his birth mother, who abandoned him as a child, and that she knows he is now well and happy. As Brierley tells me: “In the media, it’s all about Saroo finding his first family. But then there’s John and I in this story too, and also Manny. And I felt it was important. I wanted to have the circle of life flowing through.”

• Lioness by Sue Brierley is out now through Viking

• In Australia, the national family violence counselling service is on 1800 737 732. In the UK, call the national domestic abuse helpline on 0808 2000 247, or visit Women’s Aid. In the US, the domestic violence hotline is 1-800-799-SAFE (7233). Other international helplines may be found via www.befrienders.org