She was born in High Wycombe, raised in Germany and now her scandalous novel about sex, personal hygiene and almost every conceivable part of the female anatomy has taken the Teutonic literary world by storm. Charlotte Roche found the inspiration for it while sitting on the loo in a girlfriend's flat.

Even the cover makes it pretty obvious that her book is designed to provoke. Its jacket is coloured shocking pink and the title is picked out in the sort of pseudo Gothic script, normally associated with German neo-Nazis. Above it is a piece of medical sticking plaster, which looks as if it can be pulled off the cover by hand – but in fact forms part of the jacket.

In German the novel is called Feuchtgebiete – a title which will be translated into English as Wetlands when the book is published in Britain and America early next year, although the term really means the moist areas on the female body.

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It is the unashamedly shocking aspect of Wetlands that has turned the book into Germany's current runaway literary success. Since the novel was published in February this year it has topped the best-seller fiction lists, with well over a million copies sold. It has become the only German book to top Amazon.com's global best-seller list, was recently translated into Dutch and is now doing almost as well in Holland.

The novel is both an assault on the sexual and behavioural taboos that inhibit young men and women and an at times excruciatingly explicit account by the female narrator of how she goes about systematically breaking them. Granta even suggested earlier this year that the work evoked Germaine Greer's The Female Eunuch but several German critics have dismissed it as pornography.

The saga opens in a hospital ward where the heroine, 18-year-old Helen Memel, is about to undergo surgery after badly botching an attempt to shave around her haemorrhoids. Graphic accounts of masturbation, menstruation and lesbian encounters with prostitutes fill the novel's pages from then on. Yet Memel never leaves the confines of the hospital as she reflects on female sexuality.

Roche, a successful 30-year-old television presenter, says that Memel is her alter ego. She was born in the home counties to British parents. But the family moved to Germany when she was young after her father was given the job of setting up a Mars bar factory in the state of North Rhine-Westphalia. She was educated in Germany and went on to present and write programmes for the Viva, Arte and ZDF television channels. She speaks fluent English, with the tiniest hint of a German accent.

She was given a sizeable advance for a novel, while still working as a presenter, but admits that she never found the inspiration to write anything until she slipped into the lavatory in her best girlfriend's flat in the very Catholic city of Cologne.

"When I'm on the loo, I end up reading the blurb on every product I find in there to pass the time," she told The Independent. "On this occasion, I picked up a tube of soap and was shocked to discover that it was designed specially for cleaning the vagina. I began to think – my God, am I the only person left who doesn't use pussy soap?"

She came to the conclusion that a lot of women of her age must have a very messed-up attitude towards their own bodies and had become hygiene-obsessed. Wetlands is her counter-attack. It is the debunking of what Roche perceives as the sanitised, Americanised cleanliness rules that millions of women obey daily without even a thought.

On the face of it, it is strange that this kind of social criticism has emerged in Germany, the country renowned outside its own borders for its apparent sexual tolerance, its mega brothels, and penchant for naked bathing. Not so long ago it was German women above all who foreigners sniggered at for having hairy armpits and legs. "Not any more," insists Roche, "I know people of my age who won't sleep with each other unless they have removed all the hair from their bodies apart from what's on their heads," she adds. She cites the recent furore that erupted when the Hollywood actress Julia Roberts was pictured exposing a hairy armpit, as a classic example of US hygiene oppression.

A lot of young German women appear to agree with her views. On a wet evening last Wednesday, Roche appeared on stage in a converted slaughterhouse in the provincial German town of Soest to read from her novel. The auditorium was packed, mainly with young women in their twenties. Roche, who is disarmingly small and sometimes speaks with a little girl's voice, asked those who had read her book to put their hands up – nearly all of them had. "So you've turned up to hear the filth all over again and first hand – well you won't feel like having supper after listening to this," she exclaimed to fits of giggles.

Susanne Ahlers, a 25-year-old trainee teacher, agreed with everything in the book. "Charlotte Roche is so right – we live in a world in which even having sex has become commercialised and controlled. Most women aren't even aware of it, but it makes me sick," she said.

The novel's explicit descriptions were the reason behind Roche's failure to sell her manuscript to the German publishers Kiepenhauer and Witsch who had commissioned the novel. "They told me they could not possibly print it because it was pornography," she recalled. So she took it to the Dumont publishing house in Cologne which snapped it up. After successfully marketing Wetlands in Holland, a decision was taken to publish in Britain and America.

A specialist has been called in to translate all the terms that Roche has invented for parts of the female anatomy she describes in such detail; "Cauliflower" for piles and "pearl trunk" for clitoris are just a couple of examples. The author is desperate to avoid "hard words" that might offend the squeamish Brits. Her guiding principle? "When it comes to sex and sexuality – I think virtually every kind of taboo is wrong," she maintains.