Hebrew has no word for “history”, says author Heather Morris. Ivrit either borrows the English word, or uses “remembrance” instead. Or so a rabbi once told her. Certainly, remembrance and history form the core of Morris’s bestseller, The Tattooist of Auschwitz and its just-published sequel, Cilka’s Journey.

Now 66, Morris was “an average student” and went to university late, as a married woman with three children. In her forties, she became a competitive athlete — her favourite event was hammer throwing — and began taking screenwriting courses. Then she met survivor Lale Sokolov, who chose her to tell the story of his time as a camp tattooist. He selected Morris specifically because of her lack of Jewish background. No-one Jewish, he felt, would be able to approach the subject without preconceptions.

Morris intended to self-publish 100 copies and give them away to friends. Instead, more than 3,000,000 have been sold, in 53 countries, winning armfuls of awards, and a mini-series is planned for the UK and Europe. Sokolov’s family receives a percentage of profits and a share is also donated to Jewish charities.

It is hard to get her head around such success, says the Melbourne-based author. “I don’t even try. I’ve received thousands of letters from people who have read the story and been touched by it.” Why does she think Tattooist resonated with so many people? “It’s easier to relate to one person than to six million who died. It’s a one-man, one-woman one story.”

Though some critics carped at the novelisation of history, Morris had Sokolov’s full support.

“I originally wrote Tattooist as a screenplay, using conversation and dialogue to bring out the storylines Lale gave me; he absolutely approved of that… Individual stories, like Lale’s and Cilka’s, go hand in hand with academic [accounts]; they support each other.”

The subject of her second book, Cecilia (“Cilke”) Klein, was born in East Slovakia and deported to Auschwitz as a teenager. She saved Sokolov’s life and was described by him as “not ‘the bravest girl’ but ‘the bravest person’ in the world”, says Morris. “She was responsible for him and [his beloved wife] Gita being together for the next 50 years.”

Cilka’s stepson last week called the new book “lurid and titillating” adding that it was “appalling and extremely hurtful”. Morris’s publisher responded that: “Heather is a fiction writer, not a historian.”

His criticism came after our interview, in which Morris stressed her deliberations about representing Cilka. Cilka had stayed alive by “effectively being a sex slave” to Schwarzhuber, a commandant of Auschwitz-Birkenau. She had also been put in charge of Block 25, from which women were sent to the gas chambers.

Morris searched survivor testimonies for reassurance. “Did they comfort me? No, they did not. I found conflicting comments such as: she did bad things to survive, she gave me extra rations when she found out I came from the same town as her; she yelled and screamed at the condemned women; she smuggled me food when she was certain I would die of hunger”.

The author concluded that Cilka was after all very young and “you did what you did in order to survive…” Contemporary judgment of Cilka was not so forgiving. When the camp was liberated, the 16-year-old was accused of being a collaborator with the Nazis and sentenced to 15 years in the notoriously tough Vorkuta Gulag, in Siberia, a coal-mining hub where about 2,000,000 people were imprisoned and around 200,000 perished between 1931 and 1957.

Cilka’s Journey gives a memorable portrait of the minutiae of women’s lives in the gulag. Morris has a fine eye for the way they managed their meagre food supplies, pulled threads from their bedding to use in sewing, or strips from blankets to make eye masks so they could sleep in the White Nights, when the sun never set — and even helped each other give birth.

Morris feels it is important to break the silence about women’s experience of war — including sexual abuse and violence.

In the camps, such crimes were glossed over, she says, since they were not official Nazi policy. In the gulag, many of the male “trusties” (sort of prisoner-prefects) took female prisoners as mistresses and pregnancies were common. Mothers were allowed to keep their children for just two years and Morris gives a heart-rending insight into the gulag nursery.

Cilka’s situation, notes Morris, is paralleled today around the world, for instance in parts of Africa and in Bangladesh. “Women being seen as spoils of war. They were raped — why can’t they see it as what it is? Exploitation of young girls and women needs to be called out. The novel tells the story of Cilka but there are millions of others.” She’s pleased the book will appear in Russian.

For her first book, Morris had been able to interview Sokolov. But Cilka had died and the subject of the gulags was “absolutely unfamiliar. For Cilka’s Journey I had to learn a lot more myself and that was fine with me.”

She did not trek out to the location of the gulag — it was a two-day train trip; there was no way of getting there by air —it was 160km inside the Arctic Circle. But she journeyed to Slovakia several times. There she saw the records of Cilka’s birth and school life, visited her grave, the synagogue where she would have worshipped (now in ruins) and the street where her family lived (it seems none of them survived the Holocaust except Cilka).

“I used an expert in Moscow to give me information specific to the gulag Cilka was in and read testimonies,” says Morris. “I was able to imagine and tell the life she would have endured, her day-to-day existence.”

As with Tattooist, she blended fact and fiction, a process also outlined in the afterword. “Determined to tell Cilka’s story, to honour her, I found a way to weave the facts and reportage of her circumstances with the testimonies of others, particularly women… I created characters based on what I discovered through reading and research into what life was like in these camps.

“There is a mix of characters inspired by real-life figures, in some cases representing more than one individual, and characters completely imagined… The challenge of working with history is to find the core of what is true and the spirit of those who lived then.”

Cilka worked in the gulag hospital, a safer job than the hard labour performed by most of the women outdoors. A female doctor, called Yelena in the book, protected her by training her as a nurse and obtaining better accommodation for her. Yelena’s real-life counterpart (name unidentifiable from records, because apparently there were so many female gulag doctors) remained friendly with Cilka in later life.

Morris’s own experience is evident in the hospital chapters. “I worked for 20 years in a hospital in Melbourne, in the social work department,” she says. “I’m very proud to be part of an incredible team in a cradle-to-grave hospital. It has given me the skills and knowledge to listen —listening is how we get stories; that’s the only way.”

The skill Morris brought to hearing about patients’ conditions has served her well when recording the stories of survivors. In the book, she gives this listening skill to Cilka — part of the reason she survives is because she is adept at recording the patients’ symptoms.

Morris’s success and the travelling involved means she cannot spend as much time as she might like with her three children and five grandchildren in Australia.

“But how lucky am I to have them,” she exclaims. “To me, it’s important that I have to keep Lale’s and Cilka’s stories alive — I have a responsibility to continue to tell their stories.

“I hope more people will access their stories. They have been recorded in testimonies and archives in the US and at Yad Vashem and maybe others will dig them out.”

There is one other story that she is “seriously considering” writing herself, but she will not reveal more.

Surely inhabiting these traumatic memories must take its toll? “I don’t think so,” she says. “Nobody’s pointed out that I’ve got more wrinkles than when I started. I feel invigorated.”

After all, for Morris, this is a story about life.

“Cilka was not defined by the horror and the evil. I never use the word victim when I talk about her and I will not. I want readers to embrace the young girl who became a woman, who had a wonderful life and happy life, who was loved and loved in return.”

‘Cilka’s Journey’ by Heather Morris is out now in hardback, eBook and audio (Zaffre). She is touring the UK and will be at the London Literature Festival at Southbank Centre on Tuesday October 22. Visit her website for more information.