Bad hair day? Hangover? Wondering if you'll ever get a man, and whether that self-help book will really help? Congratulations, you are probably also making tons of money for the author who created you. The trials and tribulations of the 30-something single woman are the phenomenon du jour of publishing. Following the success of Bridget Jones, next week comes Straight Talking, the story of Tasha, a 30-year- old television producer. Does My Bum Look Big in This? The Diary of an Insecure Woman, a spin-off of The Fast Show, follows. The cartoon series Pond Life, featuring Dolly Pond "a 20-something neurosis-driven pint-drinker" will be back on Channel 4 this Thursday, with the video released at the end of September. It seems you can't escape a scatty Nineties woman who is frantic about being single, in a book or on a TV set near you.

But while their characters may lead disorganised lives, their creators plainly do not. Marian Keyes struck publishing deals worth more than pounds 425,000 for Lucy Sullivan Is Getting Married, published this May. Jane Green, a journalist and author of Straight Talking, says that Heinemann/Mandarin's six-figure offer was "so good I couldn't turn it down". Arabella Weir, who wrote Does My Bum Look Big in This? after playing the Fast Show character on which her heroine is based, says that there was a "bidding skirmish" for her book, ending in an advance which, while "not quite John Le Carre", was enough for her to live on for a year without having to do anything else.

First thought is, Damn, why didn't I think of this myself? Second is, how did these characters replace the glitterati in women's fiction? Most of us grew up on Jackie Collins, Judith Krantz and Jilly Cooper - women who lived in rich, jet-set worlds and had amazing sex, and whose beautiful clothes showed their size 10 bodies off to perfection. But most of us found there was little like that in real life. Neither did many live in the picturesque villages of the Aga sagas, with the Land Rover, adorable dog and village fete. Now we are confronted with women who lead chaotic lives, who hope for much and often fail to achieve it.

Oliver James, the clinical psychologist who recently presented The Chair for the BBC, thinks that the success of this new wave of commercial fiction reflects the situation young women find themselves in. "During the Seventies and Eighties surveys increasingly showed there was a serious gap between what young women aspired to and felt entitled to, and what they actually got." he said. "There has been a huge increase in dissatisfaction amongst young single women.

"We are talking about your expectations exceeding what you achieve. There has been a 10-fold increase in major depression amongst 25-year- olds. Bridget Jones is a very graphic account of it."

"I think these books are a reaction against the terrible materialism of the Eighties," says Marian Keyes, author of Lucy Sullivan and a former law and accountancy student. "People are more introspective than they used to be and this is reflected in the fiction."

Both she and her fellow authors point to Nick Hornby's Fever Pitch and High Fidelity as paving the way for these books. For while Hornby may have borrowed the confessional mode from women's magazines and tabloids for his descriptions of failed relationships and difficulties with parents, his injection of self-deprecating humour made the female "warts-and-all" book possible.

Marian Keyes and Arabella Weir both say that the main inspiration for their books was their own lives "It's based on me, and the life I lived in London as a single girl," says Keyes. Green says that her book was written after observing her friends. "I think we almost had to wait until these women writing novels reached their early 30s to write realistically about the value of female friendship, their hopes and fears for their careers," says Lynne Drew, editorial director of Heinemann. "This couldn't be written by a 24-year-old or by a 45-year-old."

Like High Fidelity, the majority of the new books make use of comic writing and self-deprecation to drive their points home. "Went to sales, gave up after two shops," moans Jacqueline M Pane, heroine of Does My Bum Look Big in This? "Everywhere I went I knew the assistants were thinking `Oh please, why are you bothering to spend money on clothes, tents from Milletts would be more appropriate."

One of Dolly Pond's top survival tips is "Ignore the ads. Periods don't have to be spent roller-skating and laughing with your mother. It's normal to lie on the sofa groaning with a hot-water bottle down your biggest pants." Candy Guard, creator of Pond Life, says: "I wanted it to be observational humour, which women find funny. It's not aggressive humour, it's more, `If I'll admit I'm like this, you're admitting you're like that too, by laughing ...' Women talk about their boyfriends, about wanting to be successful, in a humorous way. There is a definite way of looking at it, rather than the Cosmo idea of feeling terrible for being an female not achieving everything."

Indeed such heroines - with the exception of Tasha in Straight Talking, whose portrait is drawn with a much harder edge - are not likely to achieve that much. They are the sort of girl who falls asleep with her contact lenses in, agonises over her weight while managing to drink to excess, has a strong network of female friends and is continually trying to improve herself and her lot.

Most important of all, however, is that the heroine is single. While Jilly Cooper and Jackie Collins's heroines have men jumping on them every 10 seconds, and Joanna Trollope's heroines still manage a fair bit of good sex in between the Agas and the school run, these new heroines have meaningless sex and agonise over why they don't have fulfilling relationships. They are what Tasha terms "passion junkies" - they "go from one passionate relationship to the next and wonder why none of them is Mr Right".

"I was never meant to be single at 30," is how Straight Talking opens. "What I'd really really love is a chance to walk down that aisle dressed in a cloud of white and let's face it I'm up at the top there gathering dust."

Remarks such as these have opened the genre up to the accusation that these are nothing more than ditzy bimbos whose prime concerns are how to rid their thighs of cellulite and snare a commitment-friendly man. The authors dispute this.

"An intelligent woman living in a post-feminist world still recognises the basic human need for a partner, and should not feel she has to apologise for that," says Marian Keyes. "You can be massively together at 30 and not have a man," says Jane Green. "I didn't want to do a disservice to these women. A lot of books before this hadn't had women who had careers; they just had play jobs. In these books a woman's career is just as important as her love life."

"If you have grown up over the last 30 years you have grown up with feminism in your consciousness," adds Lynne Drew. "These are books by intelligent women for women."

She admits, too, that they are, at the end of the day, commercial fiction - they are meant to be enjoyable rather than political. "A lot of these books appeal to people who don't necessarily read Middlemarch or A Suitable Boy," says Arabella Weir."I just wanted to create a woman I'd recognise," adds Marian Keyes. "A woman who makes mistakes, and doesn't always have clean knickers in the morning"