Cecily von Ziegesar is thinking about growing up. “I’m not sure how much you really change in between being a teenager and an adult,” she says from the opposite end of a bench in a small park in the Cobble Hill area of Brooklyn, where we are surrounded by expensive carriage houses and brownstone town houses. As the creator and author of Gossip Girl, the 13-book series turned television phenomenon about rich teenagers living in New York’s Upper East Side — the most elite and class-conscious neighborhood in Manhattan — the author is an expert on adolescence.

The Zeitgeist-defining show, which ran from 2007 for six series, was like a Sex and the City for millennials and epitomized a certain Noughties excess that now seems almost quaint. The lead characters, teen socialites Serena van der Woodsen (played by Blake Lively) and Blair Waldorf (Leighton Meester), would show off their It bags on the steps of the Metropolitan Museum of Art, before making an appearance at their private girls’ school, Constance Billard. The clothes on the show were so influential that the costume designer Eric Daman, who had first worked on Sex and the City with Patricia Field, became a frequent figure in the press, while The New York Times called Gossip Girl “the first [show] to have been conceived, in part, as a fashion marketing vehicle”.

Meanwhile, the show made A-list stars of its cast, who would frequently be mobbed in the street while trying to film in Manhattan. But its following wasn’t just rabid teens; the show’s humor and drama — and Kristen Bell’s narration as the voice of the notorious society blogger Gossip Girl — was arch enough that people well into their thirties loved it. New episodes airing became a cultural event; every week a duo of writers at New York magazine would analyze each episode. The series was shown in 197 countries and there were four spin-offs.

Across the River

Cobble Hill — the neighborhood where von Ziegesar, 50, has lived with her English husband, an executive at an art foundation, and two children since 2006 — is the setting of her forthcoming novel. The neighborhood, which she describes as the New York equivalent of Islington or Primrose Hill, is full of quaint-looking houses that cost well into seven figures. There are chichi boutiques, yoga studios and more than one French bakery. Yet von Ziegesar looks positively unassuming in black skinny jeans and a denim jacket.

The first Gossip Girl came out in 2002 and became a New York Times best seller just as her first child was born. Rather than being an It author on the scene, she was home with a baby daughter and cranking out two books in the series a year. “I had to adhere to a strict deadline that could not be missed. I cannot tell you how many Christmases and holidays with my kids I’d just be typing away,” she says now. She wasn’t involved in the TV series, but she gave the producers her tour of the Upper East Side. And she watched it — partly because she had to. “The producers asked me to live tweet during the show. So it was kind of like an assignment,” she says. But she loved it: “Better than my wildest dreams”.

Now, with Cobble Hill, she’s skewering a new social set: upper-middle-class parents rather than teen socialites. The novel follows families in the area whose lives intersect: an aging rock star and his depressed wife; an eccentric artist and her inventor husband; and a British novelist and his American editor wife who have just moved to Brooklyn from London. This is a book with a lot of professionals covertly smoking weed and sitting around in dressing gowns pretending to work: instantly recognizable and bitingly funny to anyone who has lived in bourgeois-bohemian enclaves around the world. It’s a neighborhood where dads wear matching Ramones T-shirts with their toddlers and women wear $400 cashmere sweaters embroidered with activisty slogans like “Give a damn”. Where Ethan Hawke can be found eating ice cream or giving his daughter pep talks about her career in Scandinavian-style coffee shops.

Von Ziegesar wanted to explore the grown-ups around her who have money and responsibilities, but who act like adolescents. “I don’t really know where that demarcation is,” she says. She counts herself among them. For example, her daughter had to be at school at 7.45am. “And she’s totally put together, down to the curled eyelashes. Meanwhile, I’m in a bathrobe with my coffee, like, ‘Have a good day.’ I don’t manage to get out with the dog until 11. And it’s easy as an adult to live in a bubble. I don’t even necessarily talk to anybody all day.”

It’s a neighborhood where dads wear matching Ramones T-shirts with their toddlers and women wear $400 cashmere sweaters embroidered with activisty slogans like “Give a damn.”

If von Ziegesar is digging for inspiration in her current life, when it comes to Gossip Girl, it would also be easy to think that she was simply chronicling her own adolescence (not least because her aristocratic German last name is suspiciously similar to Serena’s). Growing up she attended the Nightingale-Bamford school, an exclusive Upper East Side private girls’ school founded 100 years ago, where annual tuition costs about $56,000 and alumnae include the fashion entrepreneur Olivia Palermo.

Cecily was born in New York to Franz Albrecht von Ziegesar, the late chief executive and chairman of Bowne & Co — one of the oldest publicly traded companies in America until its acquisition in 2010 — and his second wife, Olivia James. She is, of course, tired of the autobiographical assumptions. “I don’t know how often male authors get asked these weird personal questions that women authors get asked about their fiction. It’s sort of insulting, like the idea that women would just be taking verbatim everything that happens to them.” She says this not in a way that’s peevish, but more searching, like it’s something she is genuinely trying to work out.

Reminiscing about Gossip Girl reminds her of a strange fact. It Girl, a spin-off book series set at a boarding school (she didn’t write it, but was heavily involved), featured on its cover a teenage Hope Hicks, who is now Donald Trump’s aide. “Isn’t that ridiculous? Isn’t that so funny?” von Ziegesar says, giggling. “I mean it’s not funny, I don’t love that I have any connection whatsoever.”

In 2020 the world of Gossip Girl feels a long way away, and the people I know who attended elite Manhattan private schools and spent their teen years in the same milieu will only roll their eyes at the show, saying it was nothing — nothing — like that in real life. Still, many of them did have Chanel bags before they could legally drive, and can name several friends who disappeared to rehab for a few months and who threw giant parties at their country houses while their parents went on lavish holidays without them. But it remains a gilded memory for its fans. “I’ve had a few people tell me recently that they started rereading the books or watching it again just to see New York when it was at its best, not in the way it is now,” says von Ziegesar. The show is currently streaming on Netflix — its pandemic comfort appeal reaching a new Gen Z audience.

There is a Gossip Girl reboot in the works that the show’s press release teases: “Eight years after the original website went dark, a new generation of New York private school teens are introduced to the social surveillance of Gossip Girl. The prestige series will address just how much social media — and the landscape of New York itself — has changed in the intervening years.” Kristen Bell will once again voice Gossip Girl, though the show is facing Covid-19 production delays.

Perhaps von Ziegesar will have a cameo in it. She could be just another smartly dressed woman walking her dog down the leafy streets of Cobble Hill, looking as if she’s minding her own business — but really, she’s taking note of the habits of the area’s residents. Rich parents, prepare yourselves for grown-up Gossip Girl. XOXO.

Cobble Hill, by Cecily von Ziegesar, is out now from Atria