Emmy Award-winning journalist Ramita Navai left the city of her birth at the age of six to live in Britain. But she never forgot Tehran's magnetic pull. Returning there as a foreign correspondent, in 2003, she discovered a society bubbling with change and excitement.

Traveling up and down Tehran's main street, Vali Asr, she heard the stories of ordinary Iranians forced to live extraordinary lives: a mullah and a prostitute; a student blogger; a porn star; and a devout admirer of Supreme Leader Ayatollah Khomeini. The result is a frank, startling, sometimes shocking glimpse inside the Iran outsiders never see.

Here she talks about lying for survival and sex as an act of rebellion; why she loves surfing Find-A-Fatwa websites, and why, despite the oppressiveness of the regime, most Iranians fear sudden political change.

Right at the beginning of your book, City of Lies: Love, Sex, Death, and the Search for Truth in Tehran, you say, "In order to live in Tehran you have to lie." Can you explain what you mean?

In Iran you live two different lives. It's a kind of schizophrenic society. There's an inside, private life, and there's an outside, public life, and nearly everybody lives by these rules. You're two different people. So on a basic level, you have to lie about who you are when you're in public or when you're in private, depending on what kind of social group you've grown up in and you live in. And that filters through to every single aspect of people's lives.

So, for example, many people in Iran drink. There isn't a corner of Tehran where you don't find booze. Yet of course you have to lie about it, otherwise you'll get in trouble. So you need to lie, either to circumvent the laws or to avoid being judged by society.

Conversely, you say the truth is "a rare and highly priced commodity to be handled with great care." Can you give us some examples?

In such an oppressive environment, everything is heightened. Friendships mean that much more; relationships are that much stronger. Trust is everything when you can get in trouble so easily. So you have to be careful whom you let close, and whom you trust. I've spoken to girls who have had best friends for years but who still don't feel that they can trust them to tell them that, for example, they're not a virgin anymore. When you do share the truth, it's with immense trust. You're giving someone else a bit of your soul to look after.

You chose, as your focus, one street in Tehran—Vali Asr Street. Give us a quick geography lesson.

Vali Asr is a bit like a magnificent French boulevard, with thousands of sycamore trees lining it and drainage ditches that gush water straight from the mountains. It's about 12 miles long and runs north to south, so it connects two very different worlds: poor, working-class south Tehran and rich, gentrified north Tehran. It's a microcosm of the city.

What I love about it is its equality. Vali Asr is for all Iranians, from all walks of life, and everybody in Tehran will intersect with this road at some point. It's where people gather to protest or march, to celebrate or to shop. Ask any Tehrani what their favorite road is, and nine times out of ten they will tell you Vali Asr Street.

Your book describes "ordinary Iranians forced to live extraordinary lives." Can you explain that paradox a bit?

Stories that would seem ordinary anywhere else are extraordinary in Iran, simply by viewing them through the prism of this oppressive environment. Everything becomes more extraordinary because of how Iranians are forced to evade social strictures and the many rules and laws.

One of my characters, Amir, is a student blogger. But both his parents were executed. He then has an extraordinary encounter with the judge who condemned them to death. That's just one example of an ordinary person who has lived through extraordinary times because of Iran's history.

Your book takes us, literally, into the bedrooms of Tehranis. How did you get this much access?

I had amazingly frank conversations with people, which sometimes surprised me. Like sharing really intimate thoughts and feelings with a very conservative, religious, young Iranian woman. She wears the chador and cries whenever the supreme leader comes on television. She's absolutely dedicated to the regime. But we talked about masturbation: how she feels about it, if she thinks it's wrong, how she fights lustful feelings.

It helped that they viewed me as one of them, as a Tehrani. [Laughs] And that I speak like a whiskey-swilling truck driver. On the other hand, they saw me as an outsider, someone Westernized, so they felt that I wouldn't judge them, especially when it came to having frank discussions about sex. I think they felt: OK, Westerners are all promiscuous and are always having sex, so she won't judge me for my sex life or my private thoughts and fantasies. As a foreign correspondent, trust is everything. And connections. But I wouldn't have been able to write this book without lots and lots of Iranians helping me.

Tell us your own Tehran story.

I was born in Tehran, but I grew up in London. My father was in the navy, and he met my mum while on a training course in London. He was then posted back to Iran in 1978. My mother and my brother, who in the meantime had been born in England, decided to join him and start a new life in Tehran. We landed on what turned out to be Black Friday, which was really the beginning of the revolution, when protesters in Jaleh Square were shot down. After about nine months we returned to England; my father stayed on, and he joined us a few months later. I was six years old when we returned to London. I went back to Tehran in my late 20s for a family holiday and then again when I was 30, to work.

One of the female characters, Somayeh, spends time surfing "Find-A-Fatwa" websites. Do they really exist?

[Laughs uproariously] Yes! There are these Find-A-Fatwa websites, which give me endless delight! If you have a problem, or a moral question, you can look them up.

Somayeh had looked up masturbation: what to do if you get the urge to masturbate. The Find-A-Fatwa website told her that she must fast and pray. If it's Ramadan, and you feel you may have broken your fast by having lustful thoughts, you can pose the question to a Find-A-Fatwa website, and you'll be given your answer. [Laughs] There are even FAQs! [Laughs] It's, like, moral guidance on a search engine.

You say "sex is an act of rebellion in Tehran." How do you mean?

Lots of young people tell me that only in sex do they feel really free. There are so many restrictions and rules placed on them. The state is so determined to oversee even the minute personal details of its citizens' lives.

But as one young Iranian told me, when we have sex, it's a big, one-fingered salute to the system. No matter what rules and regulations you impose on me, I will do what I wish with my own body. What's happening among youth in Iran is really interesting. There seems to be this sexual awakening, and not simply among the rich upper classes. It's sweeping across youth in the whole country.

And it's fascinating how young Iranians get around the legal and social restrictions placed on them. In many parts of society, you're still expected to be a virgin when you marry. So, of course, there are ways that young women get around this, like having your hymen sewn up. [Laughs] One of the doctors who secretly performs these operations is known to Tehranis as Doctor Sew-Up. You can also buy virginity kits from China. You insert a kind of capsule, which bursts on penetration and fake red blood oozes out.

You explain in the notes at the back of the book that to protect your sources, you disguised the real names and locations of your characters. Can you talk about your method? And the risks for the people involved?

In quite a few cases people were very scared to tell me their stories, for fear of being identified. So we would agree together on details that I would change to protect them. Or, for example, where they were not comfortable with me interviewing their mother or their husband, we would agree on somebody to interview who came from the same kind of background and area in Tehran.

I worked a lot with my characters, because I wanted to feel as close to them as possible. Sometimes they would introduce me to somebody within their family or within their social group who would be happy to be interviewed, and I would then use that testimony in the stories. Everything I have written is testimony from someone. It's real, and true, and still happening. But I melded stories together, and created composite characters, in order to protect people.

Will they ever be able to read your book?

I hope so. Two of them are reading it now, though they're not in the country at the moment. I don't know if there are copies in Iran. It's not translated into Persian, so most of them wouldn't be able to read it.

You describe one of your characters, the prostitute Leyla, having sex with a prominent judge and a mullah. Will there be repercussions for you for being this critical of Iran's ruling elite?

I hope not. But these are not things that haven't been written before, that are shocking if you live in Iran. I didn't write them to shock. I wrote them because they were stories that were told to me repeatedly. I didn't go searching for anything. These are just conversations that happened. What I wanted to do was give the reader a taste of Tehrani life—what it's like to live there, how Tehran feels and smells, what it's like to love in Tehran with all these restrictions. What day-to-day living there is like.

The book is very critical of the Iranian regime. But, ultimately, it's a declaration of love for the people of Tehran, isn't it?

I don't know if it's critical of the regime. I think it's how you interpret it. I never set out to express a political opinion, to be critical or sympathetic. I simply wanted Iranian voices to be heard, [to] tell Iranian stories. I tried very hard to be balanced and represent society, because Iranian society is not all against the regime. There are many parts of Iranian society that support the regime. That's why I wanted to speak to characters like Somayeh, who love the supreme leader and absolutely believe in the Islamic regime.

I also wanted to show that the Islamic regime has been good for many people as well, that the revolution happened for a reason. There were many people who felt disenfranchised, and when the revolution happened, for the first time they felt part of society. They felt accepted in their own country, when they had been made to feel ashamed or socially inferior because they were religious, or because they wore the chador. So I hope it doesn't come across as critical. It's not meant to be.

And you're absolutely right. For me, it's a love letter to my city, and what I love about it: the irrepressible warmth of that city, of the people, their hospitality and the fact that people are so hell-bent on being true to themselves. They are the most resilient, adaptable people I've ever met.

Ultimately, it's the kindness. What I always take from that country and the city I was born in is kindness. I have felt kindness from all Iranians, from die-hard regime supporters to your secular, posh, north Tehranis. It's one thing that all Tehranis have in common, that Iranians have in common—their warmth and kindness.

The election of Rouhani as president in 2013 suggested an easing of repression. Who do you think will ultimately win in Iran—the mullahs or the modernizers?

This is an interesting question. What I've noticed in the past ten or so years that I've been traveling to and working in Iran is that people have shifted in their opinions about what they want to happen. I think people have looked at other countries in the Middle East—the Arab Spring, Syria, Iraq, and also the brutal crushing of the 2009 protests in Iran—and they're really scared of a bloodbath, that if reform happens too quickly it will lead to trouble. Many Iranians I've spoken to believe very firmly that change should come from within. And they're resigned to the fact that it will probably happen very slowly.

Who will win? I don't know, but I do think it will be a long, slow, drawn-out process of reform and change. That said, Iran is one of those countries that is impossible to predict. Nobody saw the 2009 protests coming. Nobody saw Ahmadinejad coming. That makes Iran such an exciting country to watch. You never know what's coming next.

Is Persia's ancient culture and history part of the discourse in Tehran?

[Laughs] Despite the revolution, Iranians are inordinately proud of the great Persian empire, and it's still part of the culture. The biggest festival in Iran is Persenia, which is Zoroastrian. It's the first day of spring and has nothing to do with religion. Although it's interesting, because the state has got involved with these pagan, Zoroastrian traditions and has tried to hijack them and claim them for their own. Like the early Christians did with pagan, Celtic mythology.

So, for example, at Persian New Year, you set a table called haftsin. People lay out seven objects all starting with the letter sīn (س ). Most secular Iranians will also put out a book of Hafiz's poetry. But the state encourages Iranians to put the Koran on the table.

There is also chaharshanbeh souri, a fire festival celebrated on the last Tuesday night of the year. Bonfires are lit in the hope that fire and light will bring health and happiness. Young Iranians go crazy, setting off fireworks and jumping over the fires while reciting an old Zoroastrian saying. It's a bit like Guy Fawkes night, in England. The state always gets nervous about this fire festival. But try as they might, they haven't been able to stamp it out. It's an ancient Zoroastrian tradition.

The book ends with a portrait of a woman called Farideh, whom you seem especially close to. Can you talk about her?

Farideh's story is really the story of all Iranian ex-pats and Iranians of a certain generation who are still struggling to come to terms with the revolution and the effects it still has on their lives. Some are from ordinary families, like Farideh. Some are from old money, who lost everything when the revolution happened, but who refused to go because they felt bound to this land, their land. They're very patriotic people. On one hand, they live fabulous lives there. Others have been completely ruined or spent years going to court trying to wrest their confiscated land from the government.

Farideh regrets not going, like so many Iranians, to America or England when the revolution happened. Eventually she leaves for London. But she misses this country, her land, no matter how screwed up it is. So, she ends up returning.

And I think this is an especially powerful story for me and for all Iranian exiles around the world. It doesn't matter whether you feel the government represents you or not. You have this pull to the motherland. It's so strong. In the end, Farideh can't fight it. She realizes that this is where her home is.

What do you miss most about Tehran when you're not there?

Feeling connected to people in a way that I don't anywhere else in the world. Its craziness. I miss the people. Their sense of humor. Their warmth. Their hospitality. And I miss the beauty of the land. It's an incredibly stunning, beautiful country.