“I have never felt more alone in my life than I did in that year,” says Caroline Baum.

As an only child, Baum was used to a certain amount of loneliness, but coming to terms with her father’s death made her feel more alone than at any other time in her life. It’s a feeling she explores deeply in her new memoir, Only.

After 40 years in journalism, founding Good Reading magazine, and contributing to various anthologies, this is Baum’s first book. It is a memoir about being an only child but it is also the story of one woman dealing with the life and death of a very difficult father.

Before Baum knew or understood the depth of both her parents’ childhood traumas, she only knew that her father’s domineering and obsessive behaviour seemed magnified by her lack of siblings. This isolation only increased with age as the responsibility for managing her increasingly frail parents fell entirely on her shoulders.

“I didn’t think that anyone had really spoken about that – the loneliness of the only child at 50 who has to think about dying parents,” Baum says.

Her father was a child when he was orphaned after being separated from his parents in Austria during the second world war as part of the kindertransport program, when thousands of Jewish children were saved from Nazi camps by being sent on train to Britain. Many, including Baum’s father, never found their parents after the war.

Later in life, he became a “self-made man”, proudly and publicly lavishing himself and his family with material goods but cruelly controlling the actions of his wife and only daughter.

“My father was a despot,” Baum says. “He ran the house like a tyrant.” Any family activities or excursions were planned to the minute, cars were to be driven in certain ways, and music was played and appreciated to rule. The dinner table was the epitome of his dominion – Baum noted that she would have traded her mother’s incredible cooking for the love that accompanied other people’s family dinnertimes.

In one passage, Baum describes how her father yelled at her that he owned her, just as he owned the contents of their luxurious home. She was “festooned with jewellery” by him from a young age – though she is quick to point out that she believed her father’s material gifts signified a fickle kind of conditional love.

“I think privilege comes with an undertow that can be very dark,” Baum says. “‘If you behave this way and become this kind of person we will make sure you want for nothing.’ That is a dangerous pact. It took me a long time to understand the baggage that came with that and the emotional impact that had on me.”

Baum’s father developed severe dementia in the last years of his life, and was in a care facility for years before he died. She didn’t begin writing Only until years after his death.

“The situation was too painful and too up-close. I was in a war zone. It was really only three or four years later when I thought that maybe his illness would provide a shape and an arc to a memoir … Then the lens became the journey of an only child believing they’d disappointed their parents to trying to become a good daughter.”

After a particularly tense and unpleasant family holiday, when she finally had enough of her father’s domineering behaviour and her mother’s lack of understanding, Baum cut contact with both parents, and the silence lasted for several years. Their reconciliation was a pivotal moment for her, and one which she is clearly relieved occurred.

“Here are two orphans and I am going to turn my back on them,” she says, remembering the moment of estrangement. “I did have to have conversations with myself about whether I was prepared to live with that tag of being a bad daughter for the rest of my life, and whether I was prepared, if they died, to live with the regret of not having reconciled.”

Through writing her memoir, Baum believes she was able to understand her father’s complexity as a man and find a sense of forgiveness and peace that she describes as “overdue”. Nevertheless, the idea of being a “good” daughter lies at the heart of the book and Baum’s references to “sliding down the scale” from “good” to “bad” punctuate the narrative, displaying a fraught inner monologue. A simple birthday card from her mother that read “To the Best Daughter in the World” had a profound effect on Baum, something that still haunts her as she worries about how publishing a memoir affects her status as a “good” daughter.

Although she had no siblings or children of her own to worry about hurting by publishing such an intimate account of her family, she still had to navigate the complicated feelings of her mother. “She found the book painful and a certain point she told me that she stopped reading it. That she couldn’t go on.”

“My mother did say when I gave her the book, ‘Oh, so you waited for him to die, but you didn’t wait for me.’ I don’t think I have become the ‘bad’ daughter but I have become the ‘less-good’ daughter – I have lost a few points, there’s definitely no question.”

Baum describes her mother as having a traditional idea of privacy, and that many parts of the book discuss matters that her mother would rather not be shared. One of the most obvious examples is the many extramarital affairs Baum discovered her father had engaged in during his extravagant but traumatic life. The other is her mother’s own childhood trauma: her father – Baum’s grandfather – killed Baum’s grandmother in a violent murder-suicide when her mother was a child.

“I’ve violated her privacy,” says Baum. “I think she finds it very painful to be judged not only as a mother but also as a wife. I’m very sympathetic to her. She was heroically patient and long suffering for very complicated reasons but that doesn’t necessarily make the book any easier for her to read. Just this week she told me she really likes the trailer of the book and I regard that as being as close to approval as I am going to get.”

Despite her mother’s mostly negative reaction, Baum admits she could never have written her memoir with her father alive and lucid. “I could have written it when he was demented but, to be honest, I was too sad. I was still grieving.

“My father said to my mother at one stage that the greatest regret of his life was that he didn’t have a better relationship with his daughter.”

• Only by Caroline Baum is out now through Allen & Unwin