Letty was the daughter of religious parents who joined a Conservative synagogue when they moved to America. For two years she attended an Orthodox yeshiva school.

Letty was growing up frum. She recalled: "I was a very pious little girl. I studied Torah. I went to synagogue on erev Shabbat, Shabbat and every holiday. I was one of the first girls to be batmitzvah in the Conservative movement in America."

Then tragedy struck. When she was 15, Letty's mother, Cyral Cottin, died and Letty was not allowed to say kaddish for her.

She said: "When I was excluded from the minyan for kaddish, it struck me as such a gross injustice that my Jewish education counted for nothing.

"When it came time for my faith to comfort me in a moment of distress and need, I was rejected.

"I said 'if you won't count me in, I will count myself out'. I left Judaism more or less in 1955 at 15."

But Letty never really left Judaism. She just became less observant. She describes herself as "not a halachic Jew".

She said: "I am not a Torah Jew. I don't practise and keep the commandments. I am just very educated and I am very respectful of my heritage."

But she still continued to keep the festivals at home. For many years she only went to synagogue on Rosh Hashana and Yom Kippur and did not belong to a shul, although she now belongs to New York's post-denominational B'nai Jeshurun.

Although Letty stopped going to shul on Shabbat aged 15, she still cooked Shabbat meals.

She explained: "I was continuing my mother's Judaism which was haimishe. My mother was not educated. She came from a shtetl."

And strangely, for a supposedly rational-thinking radical feminist, Letty still keeps her mother's shtetl superstitions, designed to ward off the evil eye.

"My mother had a wonderful blend of superstitions," she told me. "I am positive about them. Feminism works in very interesting ways.

"When you inherit something from your mother and it's the best she can give you because she was not educated, you treasure it.

"I am very familiar with the evil eye. My mother's world of superstition involving the ayin hora was a very systemised world to keep away the devil and come closer to God.

"You came under God's protection when you rejected and rebuffed the devil. You had to wear a red string. You had to put a red ribbon on the bassinet.

"You couldn't sleep with the moon shining on you. The moon should only shine on your grave or the evil eye will think you are dead.

"You can't have something mended while you are wearing it. You should only be sewn into your shroud or the evil eye will think you are dead and come and get you.

"The idea was to repel death by using these tried and true shtetl superstitions.

"Since my mother died when I was so young, I cherish her. I still keep her superstitions. Women absorbed the traditions of their mothers and grandmothers. I honour them."

The theme of Single Jewish Male Seeking Soul Mate is intermarriage. Its protagonist, Zach Levy, is the son of Holocaust survivors who is made to promise on his mother Rivka's deathbed that he will only marry a Jewish woman to ensure continuity to make up for the millions lost in the Holocaust.

He marries a Jew, only to have her leave him for her female lover. Secular Zach goes on an unsuccessful shidduch quest, as described in the book's title, only to fall in love with a black female activist and be faced with the dilemma of whether or not he can accept a child of that union.

Topically, the book asks questions about the subject of Jewish patrilineal descent.

"Writing this book made me feel that the complexity of intermarriage is inextricably bound up with the nature of the Jewish future," Letty said.

"Either we are going to welcome children who are being raised as Jews, regardless of which parent is Jewish, or we are going to lose Jews.

"I am more interested in content, the learning, heritage and tradition. I am not interested who is with what label. I want the children to carry Judaism forward."

Most of Letty's previous books have been serious non-fiction works based on her experiences of being a woman in a man's world, sexual politics, being Jewish and feminist, ageing and cancer.

So why has she now produced such an easily accessible book, appealing to both men and women interested in Jewish identity and continuity?

"I decided to write the book more than 20 years ago when one of my daughters fell in love with a practising Catholic," she replied.

"It suddenly almost blindsided me that my grandchildren might not be Jewish. That suddenly hit me in the kishkes.

"The man was insisting the child would have been baptised and raised in the Catholic faith, genuflecting, going to church and would accept Jesus Christ as the moshiach, all of which drove me up the wall.

"I was blindsided by it because I am a very educated Jew, especially for a woman.

"Suddenly I realised that everything I believed in and all of my ancestors who died for this belief system, this heritage, were coming to a dead end with my daughter's children, if she agreed to raise them Catholic.

"It made me reconsider the meaning of my Jewish identity. There are red lines that you don't cross in terms of what has to be carried forward, that all this talk about Jewish continuity does not really grapple with the continuity of that.

"We are not all Orthodox. At this point that is a minority. What does everybody else who isn't Orthodox mean when they say they want Jewish continuity? That is what got me started with the book."

Both Letty and her daughter ended up marrying Jews, but the subject continued to fascinate her.

She said: "The book is about my internal struggle. I think I was very aware that I was expected to carry on the line and marry a Jew. I was educated as a boy would have been.

"It was not spoken to me as overtly as Rivka did in the book.

"I married a very left-wing Jew who had not been educated at all, but who liked Yiddishkeit."

She continued: "I have written many books since I first thought of the idea for this one, but it was always percolating. I had other books that I needed to write.

"I was writing this book when I got breast cancer seven years ago. I put this book aside.

"I had experiences during the cancer which made me write the book, How to be a Friend to a Friend who is Sick. I stopped everything to write that book which was published in 2013. Then I went back to this novel."

Letty became a feminist after the publication of her first book, How to Make it in a Man's World, in 1970.

She told me: "That was not a feminist book. It was really a career woman's book.

"In 1970 there were not many women who had high-powered jobs. I did. I was vice president of a book publishing company.

"I had worked my way up to that position. I graduated from college and married at 24. So I had a pretty good period of time when I could establish my career before I was married.

"My husband, Bert, was a very advanced left-wing guy. There was no need for me to stay home.

"He told me to do my thing. I loved the literary world and continued to work.

"When my twins, Abigail and Robin, were born in 1965, I quit because that is what everyone told me I had to do. But I got very bored, went back to work and had my third child.

"Then I wrote the book about my career. When it was published in 1970, the women's movement was bursting with rage.

"My publisher told me that I had to know Women's Lib because they were going to attack me as I make it sound easy.

"It was not like that for most women. She called me a queen bee.

"She told me I had to be ready to defend my career. I had to look at the broader impact of gender on women's lives and discrimination. She gave me a real talking-to."

Letty completely radicalised herself by reading feminist books and pamphlets.

She recalled: "I was bringing home all these position papers written on mimeograph machines put out by women's groups all over the country, I had a big pile on subjects like The Politics of Housework.

"I would discuss them with my husband. The two of us became feminist together. We really saw the logic, sense and justice in it."

Then, like many Jewish feminists, Letty became aware of antisemitism in the women's movement. Having been a founding editor of the feminist journal, Ms Magazine, Letty wrote a 1982 cover story about antisemitism in UN women's conferences.

She said: "Jewish identity is very important to me. I feel in the feminist and peace movements as if I am first and foremost a Jew.

"When I'm in the Jewish world I feel as if I have to carry the banner of feminism. Whatever part of my identity is most threatened, that is the one I put forward."

Single Jewish Male Seeking Soul Mate is published by The Feminist Press, £10.53.