Lurve-struck Letty Chubb, Ros Asquith’s Teenage Worrier, would be swept off her feet by her creator’s studiobedroom. Asquith’s mantelpiece is crammed with Valentine cards from family and friends and the bay window has an uninterrupted view of passing north London Lurve Objects - Boyz, as Letty spells them.

A few hours in Asquith’s company will banish the blues for worried teenagers of all ages, even thirtysomethings who still find plenty to worry about in the state of the world, the pitfalls of parties and bad hair days.

She is Letty writ large, instantly recognisable from her drawings in the Teenage Worrier’s Guide to Lurve, the latest volume of the anguished Chubb chronicles and a current Waterstone’s Children’s Book of the Month. Letty’s zest for living and her blend of pragmatism, wit and intensity are there in the flesh - the Teenage Worrier has grown out of her self-consciousness but hung on to her favourite waistcoat and her peals of laughter.

Asquith has hurled herself with Letty-like enthusiasm into several careers - photographer, theatre critic and cartoonist (she is responsible for the Guardian’s Doris strip) - since a senior colleague told her early in her photography days to take pictures for love, if not Lurve. The Teenager Worrier books are her first foray into fiction. The Guide to Lurve, in which chapters of a manic Languishing-Letty-Pursues-Hopeless-Hunk tale alternate with a subversive advice alphabet, is the best read of the series, with its romantic storyline collapsing into a denouement worthy of Ealing comedy and its post-modern shifts between narrative and commentary.

Her earlier cartoon books Baby!, Babies! and Toddler! have already milked parental crises for laughs and agony (she has two pre-teen sons). She confirms, however, that Letty’s traumas are drawn from memory, helped along by the letters her best friend sent her at 16.

“My teenage years were a vale of tears, as most people’s are. At 15, I was crying almost every day over an older man of 26. I told my mother: ‘They only want one thing - conversation.’ I learned then to make jokes about sad things, and Letty’s humour is very important.”

One intention behind the Worrier series is to dispel the isolation attached to the anxieties and embarrassment of youth and to show as timeless both the feelings and the myths surrounding teenagers, passed on intact to each generation.

“Adults have always said the same things about teenagers - that they look awful and behave badly. Sophocles complained that they didn’t stand up when the teacher came in. People are blinded by the fact that someone has a ring in their nose, and don’t listen to what they have to say. The media in particular is very obsessed with modishness, fashion and slang, or with teenagers as a problem group, and the soul of the teenager is ignored.”

Letty’s soul - her spirituality, her inclination towards poetry and her blueprint for a more equal society (“End this tyranny, says El Chubb, so that all LURVers can gamble, I mean gambol, in Elysian Fields for Eternity”) - is given free rein in the Guide to Lurve. With her metropolitan street wisdom and slightly Bohemian background (working-class gran, downwardly mobile but embarrassingly snobby mother, arty but hard-up household) the Worrier is carefully pitched to draw readers’ interest without seeming out of reach. She’s also, Asquith points out, “a very moral person, although teenagers are often accused of immorality”. While the sexual content of schoolgirls’ magazines alarms MPs, Letty remains a rational virgin.

Her few weird spellings - Gurlz, Boyz and Frendz - need cause no more concern than her morals. Letty is highly literate and loves to play with language, resorting to delightfully over-the-top flowery prose to send up her more sensitive passages. Asquith allows her to pour contempt on much of the existing reading matter marketed at teenagers, such as some of the snog-and-shop magazines which Letty lampoons as “Smirk, Weenybop, TruLuv and Yoohoo!”.

“It’s quite a sophisticated book,” she says. “Letty’s audience would not normally be attracted to teenage books or magazines, which can be very patronising. But it can be read with different levels of sophistication. I had to make sure that the story worked before writing the dictionary entries and it’s fun to read through the story first, but it’s meant to be kept and dipped into.”

The A to Z sections include cautionary notes on unsafe sex - or any sex at all, in many cases - drugs, alcohol and the wearing of cardigans (beige) and anoraks (any colour). “You’ve got to get a balance between responsibility and having a laugh,” says Asquith. “I’m not an agony aunt or an expert on teenagers and would hate to be either of those things.”

She has most comfort to offer to those with an obsessional or neurotic streak (more or less everybody, she believes). “Letty can’t say the word ‘death’: she calls it ‘banana’. Death and Aids are the big unspeakable fears for everyone, especially the young. Letty also has various little ritualistic habits - she touches things twice, for example, which Dr Johnson used to do.

“I wanted to show that doing that sort of thing doesn’t mean you’re mad - you can easily think you’re mad at Letty’s age. I get a lot of letters from teenagers who think nobody else kisses their teddy good night when they’re 17. I write back, if they give an address, and tell them they’re not alone. ”

Most of her correspondents are girls. The boys who write to her either want to meet Letty or are worried about being gay. “The tragedy of being gay in school is that since Clause 28 there’s nowhere that it can be talked about openly. That’s why I’ve tried to address it in the book.”

The Guide to Lurve has sound advice for those uncertain about their sexuality and those in abusive relationships, but perhaps its most important message is the distinction between reality and fantasy; between love and Lurve. Letty ricochets between picturesquely grandiose fits of passion for the unattainable Daniel and comforting dispatches from her home front which reveal that her cat, her gran and her little brother are more reliable sources of everyday affection and affirmation. She warns against taking crushes on celebrities (or teachers) too seriously.

Asquith believes such an emotional sense of proportion is crucial in protecting young people from the risks that may follow new, highly charged relationships.

These can range from cult religions and drug abuse to thechild involvement in prostitution and pornography highlighted in a recent report by children’s charities.

“You’re very susceptible as a teenager to someone new and charming who seems interested in you, and that’s where abusive situations often start. If you start off with a sense of feeling loved by people around you, then you aren’t so vulnerable.

“Letty has this passionate obsession with a boy but her great devotion to the cat and her gran are very real - more real and sustaining than the crushes - and she is aware of how lucky she is to have all that.”

Self-esteem, then, is the lifelong cure for Teenage Worries. As the arch-Worrier herself, with another trauma-laden tome “under discussion”, would say: “How soon are the bat’s wings of despair turned into the softly beating cherubs’ pinions of hope.”

The Teenage Worrier’s Guide to Lurve is published by Corgi, Pounds 3.99