04/28/2011 at 11:00 AM EDT
Bridget Jones fans, take heart: The plucky, hilarious heroine is poised to make her return.
The wine-guzzling, weight-checking, big undies-sporting star of the 1996 smash novel Bridget Jones's Diary
and its 1999 sequel – both brought to life on film
by Renée Zellweger
– is "just turning 40," says author Helen Fielding
, who is currently writing the third book in the series.
"Bridget is struggling with baby issues – that sort of baby panic," Fielding
tells PEOPLE. "It's going to be talking about babies and life and really the theme of it is expectation: the way life never turns out quite the way you expect."
But readers who can't wait for the book can find Bridget on Twitter (@bridgetjoneshf), where Fielding voices the character in all her neurotic glory, along with Bridget's love interests Mark Darcy (@markdarcylegal) and Daniel Cleaver (@danielcleaverxx).
"I'm obsessed with it," she says. "I can only write one sentence, and then I have to Google a vacation. I knew if I got on Twitter I would not be able to stop, and sure enough, that's what's happened.
Fielding, who is also working with singer Lily Allen on a musical stage version of Bridget Jones
, continues to marvel at the affection for the series, which has sold nearly 20 million books worldwide.
"I think it's made me see the world in a slightly different way," she says, "and understand that everyone seems to have this feeling in the modern world that there's a really big gap between how they're expected to be and how they really are. And I think that's really at the bottom of Bridget."
For more from Helen Fielding – including how she juggles work and handles her life as a mom of two – pick up this week's issue of PEOPLE