Markovits, a native of France, broke away from the community, as does Atara Stern, one of the daughters of the family in "I Am Forbidden."
But most of the book centres on those who remain behind, especially the young couple Mila and Josef, whose infertility and desire for a child sets them on a collision course with tenets of their faith.
Trained as an architect and scholar of comparative literature, Markovits spoke with Reuters about her novel and her life, where they intersect and where they differ.
Q: What inspired the book? I've read that you've said 9/11 had something to do with it.
A: "I think what happened with 9/11 is that I realized even if I in my private life had (left) fundamentalism, it was out there. I knew that I had an intimate knowledge of aspects of it...The people inside (the novel) had all made choices so different from my own, and I didn't know if I could even imagine their inner lives. But I did feel that I should try, that if I were able to do it maybe I could basically lift a corner onto a world that is really not acceptable to most people in mainstream Western society.
"So I just started and it ended up being extremely difficult because it was a world that I had left, and the people were making choices that I had not done. But then it's the magic of the novel, it required that I enter these characters and inhabit them. And the more I was trying to be these people, the more I was also realizing that that very approach, where you allow conflicting voices and multiple voices to express themselves, was itself anti-fundamentalist."
Q: How old were you when you left home, how hard was it?
A: "I was 19 when I finally left. I left because in that world, people marry - arranged marriages. I felt I couldn't put it off much longer, I had to make a move or I would be married into that world and I knew that would be completely unfair to whomever I married.
That was extremely traumatic, because you really generally lose everything you have known. You lose your family, your community, your friends."
Q: How did you come up with the characters, and is there one you feel especially close to?
A: "Oddly enough, I would say that there was one character who still breaks my heart, and that's Josef. Josef is sort of the man who is almost the battleground and the person who is annihilated by extreme forces and conflict and divided selves. I would say that he's a character that I feel I could have been, I feel that I'm happy that I'm not. Of course Atara is in some senses the character more closely modeled on my trajectory."
Q: When you say that in some ways Josef and how he becomes a battlefield could have been you, what do you mean by that?
A: "In many ways I feel that every one of the characters in some sense could have been me - when I think also of what happens to Judit, who finds herself at 17 with basically no valid voice. Although the specifics of her predicament were totally not mine, in many ways this sense of being trapped... is something which many people who want to leave have. They all feel at a moment, 'I can't do it, I have no choice.' And then most of them, those who feel they really have no choice, they choose what she did. At some point you cave in and hopefully desire ticks over and life ticks over and you move on."
Q: I'm interested by what you said that as an architect, you think of the idea of force and counter-force.
A: "It's the idea that of course conflict drives story, and of course conflict can be internal conflict within a character. It begins with Zalman in conflict with his body. I pretty much realized as I went along that there was something about the novel that wanted a counter-force, always. So Atara had Zalman to oppose her. Mila's desire for a child is totally driving her, but her faith tells her there's nothing she can do. All along, I would say, that it was the structure on which I built the novel. But I think most novels are built that way. Every writer interprets it differently, but the principle is the same.
Q How long did this take to write?
A: "Years. I would say almost seven years. Some of those years were spent just working with the language. It was very hard to put myself in those characters, it was very hard to go there, I didn't want to make the choices that they were making. You do have to inhabit that world, and it was a world that I had left. I didn't take all that time to write the novel but I took that time to put myself in a position where I could write it." (Reporting by Elaine Lies; editing by Paul Casciato)