Her latest book, Exodus: A Memoir (Plume, £11.99), explores her paternal grandmother's Holocaust roots.

Deborah - whose mother, Shoshana Rachel Levy, was born in Manchester - wrote to the British government to obtain her great-grandfather's naturalisation papers to prove his German citizenship to the German government.

Deborah's maternal great-grandfather, Gustav (Naftali) Spielman, emigrated to Manchester from Bavaria in 1938.

"I discovered that my maternal great-grandfather got his PhD at Ludwig Maximilian University, Munich. I found his thesis," said Deborah, who is living in Berlin, where she is taking part in a film about female sexuality in fundamentalist culture.

Deborah's maternal grandparents divorced after her Manchester grandfather, Abraham Levy, became ill.

She believed that her paternal great-grandfather Chaim Levy, was "very prominent in Manchester society".

As the child of divorced parents, Shoshana Rachel, who went to Manchester's Bnos Yisroel School, was unable to find a local shidduch and was married off to a New York Satmar chassid with undiagnosed special needs. The marriage broke up.

Shoshana Rachel, who became a lesbian, left her daughter in the care of her paternal grandparents.

Deborah said: "I was angry at the story of how my parents were brought together. I always felt resentful towards my paternal grandfather for being so cruel.

"My mother suffered a lot. She was very greatly deceived. They had so much interest in trying to get a shidduch for their son, who had problems, that they didn't mind sacrificing another human life for it because they were so determined to get their way. "My mother already had a difficult upbringing, but she was a very intelligent person and had a lot of potential. I think it really broke her.

"She was born in a time when it was more difficult to achieve resources. I think she inherited emotional challenges from her family."

Despite the fact that Deborah's maternal Holocaust survivor grandmother Pearl did her best in bringing Deborah up, the mother-deprived girl felt discriminated against by her large Satmar family, who treated her strictly because she was the only one of the clan not living with her parents.

Deborah, like her mother, also entered into an early arranged marriage, which was equally unsuccessful.

Deborah left her husband, taking her son, Isaac, with her, in order to study the secular subjects which had been forbidden in the Satmar community.

Discovering that she had a flair for writing, she wrote Unorthodox.

In her book, Deborah claimed that the Satmar community was riddled with violent abuse in which "parents hit their children, teachers hit their students and rabbis claimed that the Talmud made it right".

Her theory is that the Satmar culture of "violent abuse" is a by-product of European antisemitism.

She wrote: "Authority and discipline are seen as necessary, as much to pre-empt divine punishment as to self-flagellate for the sin of surviving a tragedy that wiped out most of their ancestors.

"Suffering brought us closer to that first generation of survivors and it compensated somehow for all those who died horribly."

The book simultaneously scandalised the Satmar community and whirled her into international fame.

Deborah said: "I was surprised it did so well because my publishers Simon & Schuster, my agent and editor all assured me that my book was on a niche topic that no-one would really recognise.

"I wrote the book because I knew it would help me get custody of my son. Everyone assured me that the book wouldn't do well because it was the kind of topic that no-one would relate to.

"When the book went to print in 2012, there were only 8,000 copies. It sold out before it was released. I don't know exactly how it happened, but the book took off and became an overnight sensation.

"It wasn't available in book stores for three weeks because the publisher couldn't restock. It was so quick and unexpected that no-one was prepared, least of all myself.

"I went from being absolutely anonymous to being recognised everywhere in 24 hours. It was a huge shock. It took me a long time to adjust.

"The first thing I wanted to do was to move away from New York. I wanted to leave the place where I was so easily recognised.

"In my second book, Exodus, I wrote that I went to live in the country in New England because I wanted to be somewhere quiet."

Living in Germany is a similar experience of being unknown for Deborah.

She seems to have some strange fascination for Germany and even for German men with whom she has had several relationships in order to test out whether or not they are still antisemitic.

Walking out on her Chassidic past, Deborah cannot leave her Holocaust history behind. Exodus describes how she leaves her past, not to head for the promised land as in the Pesach story, but back to Germany, the birthplace of the Holocaust.

Ostensibly, Deborah is delving into her grandmother's eastern European roots, as any third generation Holocaust survivor might, but she is also flirting with the danger of forbidden fruit as she deliberately seeks out German men.

"In Germany, I meet people who have Nazi ancestors all the time," he said.

"It is not a rare occurrence. A lot of people feel they should let sleeping dogs lie and stay away as much as possible.

"I always have this desire to throw myself back into that dynamic and try to find the closest I can get to understanding and peace, which is unreasonable but which people should strive for.

"I find my connections with young Germans to be very enlightening, but not always satisfying."

She continued: "I recently met a young German man quite by accident when I was out with friends. He knew one of my friends and we all went out for dinner.

"I was the first Jew he had ever encountered. He had just got admitted to Harvard for a PhD for six years, but had never been to America. I told him he was going to meet a lot of other Jews there.

"He said that his grandfather was a Nazi as though he was almost looking for absolution. It is so ridiculous for so many reasons.

"He is very educated and a politically and socially responsible person with a very strong moral core. He is not to blame for his grandfather's behaviour.

"It is very interesting that he felt discomfort and guilt around me. We spent an evening together. I have a very particular way of handling Holocaust issues through humour which people find either offensive or acceptable.

"He said he was so uncomfortable when I was making jokes about Jews and Nazis. He was not prepared.

"But in the creation of a joke, there is space for two people. I never expected that I would ever be able to feel totally relaxed and OK to joke about the Holocaust. I thought that was an accomplishment."

But with all her desire to shock by playing with forbidden fruit, unlike her atheist mother, Deborah has not totally abandoned Judaism.

For Pesach she deliberately went to Israel for the first time.

She told me before she left: "I am in the process of rediscovering a kind of Judaism which fits me better.

"Europe is really an intense place to be Jewish right now. I'm going to Israel for the first time in my life next week.

"I'm in a phase when I'm seeking out a kind of Judaism that is something that is more uniquely suited to my spiritual needs."