The character, a plump, awkward and unlucky-in-love 30 something single woman, was played endearingly by Renee Zellweger in the two hit films -- 2001 'Bridget Jones's Diary' and 2004's 'Bridget Jones: The Edge of Reason'.
Zellweger put on weight to portray the character while her lovers -- a caddish publishing executive and a socially awkward lawyer -- were portrayed in the films by Hugh Grant and Colin Firth, respectively.
The book will take place in Jones' London with the character entering a new chapter of her life.
"She has grown up. I mean, my life has moved on and her life will move on too," Fielding told BBC Radio.
"And in the same way as the first Bridget book was looking at the way that a thirtysomething single woman was branded as a tragic spinster -- and then we got the new idea of a 'singleton' -- it's looking at later phases in life where you get branded as a certain thing."
Fielding found it "a bit scary" to bring out a new book but it made her laugh and she enjoyed writing it.
A third film is already being planned reuniting Zellweger, Firth and Grant. The film is titled 'Bridget Jones's Baby'.