“I’m a terrible gossip,” admits Cecily von Ziegesar, author of the mega-successful series of books entitled Gossip Girl. “I talk about people constantly.”

Centred on the lives of a group of privileged teenagers in New York, the series has sold a whopping 4.5 million copies to date and is showing no signs of relenting, with three more books coming next month, as well as the much-anticipated television series.

So gossip clearly sells – and according to Cecily, herself a native New Yorker, this is no bad thing. “Gossip is a human pastime. It’s a part of life and it is entertaining. The newspapers, even the broadsheets, are full of gossip; politics is full of gossip. It’s part of our human existence. And it can also keep us in line, you think, ‘What are people going to say about me? I better do the right thing.’”

The initial idea for the Gossip Girl books came from Cecily’s time working as a an editor in young adult titles with a book packaging firm. She was responsible for creating ideas for new book series, which were then farmed out to publishing companies. The Gossip Girl brief was given to Cecily to develop and she took inspiration from her time at New York’s Nightingale-Bamford School.

Because of this background, setting the books in the exclusive realm of Upper East Side private schools was a no-brainer: “In creative writing classes the message is drummed into your head to write about what you know, so I thought that was the best setting for me.”

Writing about teenagers might not seem the obvious choice for a 37-year-old married mother-of-two, but she says: “I think pretty much the same way now as I did when I was a teenager. It was certainly very easy for me to access that as I really haven’t changed that much.”

Spoilt brat Blair Waldorf heads up the book, ruling the teenage set along with her on-off stoner boyfriend Nate and her beautiful friend, Serena van der Woodsen.

Following the characters as they navigate the troubles of teenage life, the books are dominated by a love triangle between the three.

Creating the character of Blair was a masterstroke: her selfishness, stubbornness and complete self-obsession make her the focus of much of the humour, but while she is the most flawed of the series’ main characters, she is also the most likable.

But surprisingly she was not first choice for the heroine role. “Originally my heroine was Serena,” Cecily says. “But she’s so beautiful and nice and everybody loves her that she’s just boring. She doesn’t have all the flaws and complexities that Blair has, so later on in the books she just took over and became the main character.”

For all Blair’s bravado, she is satisfyingly human, and the things she wants – to get into the right college; to win the heart of the boy she likes; to get more attention from her parents – are normal teenage issues. In short, she is far more than the stereotypical Barbie rich girl who creeps into much teenage fiction.

Another variation from the norm is the use of blogging in the series. The success of the books in part grew from online word-of-mouth and Cecily reckons the style back when they launched was cutting edge.

“Blogging was something new. I don’t even know if the term ‘blogging’ even existed yet. Teenagers were writing about themselves online in this very honest and brutal way.

“It seemed like the logical thing to use it within a book and it’s a great literary device, allowing me to plant things in her column.”

And from online it is now on-screen, thanks to a television adaptation by Josh Schwartz, creator of The OC. Soon to beam onto UK screens, Gossip Girl has already gone down a storm in the States, a factor the author still can’t quite get her head round.

“It was thrilling to see the series,” laughs Cecily. “But I was also so nervous, my heart was pumping, it was just so weird. I was like, they’re acting out my books and I was just giggling hysterically. It was so strange.”

Fashion reigns supreme throughout, the books littered with references to designer labels. From Chloe sundresses to True Religion jeans and Marni shoes the tales read like the latest issue of Vogue.

Despite claiming she is “not particularly fashionable”, Cecily does admit to being “a chronic shopper” and to “reading fashion magazines and paying attention to it all”.

When not engrossed in magazines, she is next planning on retiring Blair & Co for a while, replacing them with the Carlyles, a set of 16-year-old triplets. While the characters may change, the voice of Gossip Girl will remain, with gossip reigning supreme as usual.

Gossip Girl 9: Only In Your Dreams; Gossip Girl 10: Would I Lie To You? and Gossip Girl 11: Don’t You Forget About Me are all published in April by Bloomsbury. The Gossip Girl television series starts on ITV2 on March 27.