The Joy of Sex by Alex Comfort is such a seminal book that even people who have never laid eyes on a copy know about the iconic bearded man and the saucy French terms, and the troubling references to vacuum cleaner injuries. When it was first published in 1972 the book didn't just reflect the new free-love, “anything goes as long as it doesn't hurt anyone” attitude to sex, it also helped to shape already changing attitudes. Since then it has been updated four times and has sold more than eight million copies in 14 countries.

Susan Quilliam, the agony aunt and psychologist who has completely updated the book for 2008, was 22 when it first came out and recalls how it touched a nerve. “The Joy of Sex was the first book I read which was sexually aspirational. Someone in my boyfriend's flat had a copy before he and I had ‘done it',” she says. “It was very useful. We did giggle but we also thought wow... All the bondage and S&M stuff was very revolutionary. In fact, one of my sadnesses in updating the book is that whatever I did I could never be as revolutionary.”

There's the rub. When the original was first published there was nothing else like it on the market: other sex manuals stuck with the science and ignored the pleasure. Quilliam's generation, caught between “parents who expected me to go to my wedding bed a virgin” and the new urgency about exploring sex, were hungry for enlightenment and inspiration.

The current climate could not be more different. Now there is almost too much advice, in books, on television and the internet; Ann Summers sells more than 1.2 million sex toys a year; and bondage on Footballers' Wives barely raises eyebrows. What purpose can be served by updating a period piece now that there are so many other great books about sex?

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Quilliam makes a good case. “I don't think there has ever been more need for education because we're living in a society which is far more sexualised than when Alex Comfort was writing,” she says. “At the same time, I know people in their thirties who still don't know about the importance of the clitoris.

“I think what a lot of the other material out there misses is how powerful sex is; people die for it, literally. One of the ways we've gone wrong in the past is that we haven't recognised this emotional power. Sex isn't a game - it's not pink and black and fluffy. So I think there still is a need for a book that takes sex seriously.”

Quilliam, 58, has perfect credentials for taking on Comfort's mantle. She offers advice on a number of websites and has written 18 books on love, sex and relationships. A former secondary school teacher, who taught sex education and English in Liverpool, she also ran a company producing personal and social education (PSE) materials for 20 years.

“I enjoy sex enormously”

She lives alone, above a shop in Cambridge, with two long-haired Balinese cats (“my princesses”). She is a workaholic, but four nights a week and on holidays to Argentina she dances tango (an appropriately fruity hobby for a sexpert), and finds there is no shortage of dance partners. When I ask about her sex life she looks momentarily evasive before briskly replying: “I enjoy sex enormously. I wouldn't be writing about it so enthusiastically if I didn't.”

She enjoys shocking “hardened gynaecologists” when she addresses medical conferences, and says: “My problem is I don't know when to keep my mouth shut. Recently I was in the pub and somebody said, ‘What is this thing about female ejaculation? I don't believe a word of it'. I said, ‘No honestly, it does exist, I know because I ejaculate', just as the whole pub went quiet. Luckily a group of guys was passing and one said very pleasantly, ‘Good for you girl, good for you'.”

Quilliam, who pronounces the word “sex” with the mildest Liverpudlian lisp, brings a much needed woman's touch to a book that was criticised by feminists because it was written almost entirely from a male perspective. There were, for example, just three references to the clitoris compared with an ample section on the penis. Then there is Comfort's old hippy take on porn, which he defined as “the name given to any sexual literature someone is trying to suppress”. And don't get me started on the “Buttered Bun”, when two men have sex with one woman.

It is a relief to see Quilliam pull a face when she mentions the bun thing, and Comfort's interest in group sex generally. He believed that within years there would be designated places where people could watch each other making love. In the post-Aids update of the book, a crestfallen Comfort described such behaviour as “suicidal”.

More emphasis on relationships

Quilliam's brief was to write the book Comfort would have written had he still been alive , so while she has retained the section on “Foursomes and Moresomes”, you can tell that she doesn't have the stomach for it. Only a few of the original entries have been ditched entirely: sex on a motorbike, the grope suit - Comfort's joke invention of a Scandin-avian garment that prompted continuous orgasm. There are 43 new sections, including phone sex, the internet, sex shops, and sex during pregnancy, and there is more emphasis on relationships.

What's missing is the often infuriating strid-ency that made the original so special. Comfort clearly felt he had to bang on “to cure the notion that common sex needs are odd or weird”. But his voice is as hard to ventriloquise as the sexual mood of the time. Quilliam puts her finger on it when she says: “Alex Comfort wrote the book on the back of the atmosphere I experienced in the late Sixties and early Seventies, of seeing sex as something like a big treasure box you were opening and taking out wonderful things. There was a real innocence. And an innocence of the hurt that can be done.”

It is hard to know whether Comfort would have regarded our highly sexualised society as progress. No doubt he would have applauded the mainstreaming of sex shops and the sheer volume of chat on the subject, but he would surely have been shocked by the paucity of sex education, a subject Quilliam cares about passionately. She would like schools to introduce weekly lessons about relationships. “Only 25 per cent of girls enjoy losing their virginity whereas the percentage is much higher for boys. That is down to biology but nobody ever tells the kids that,” she says. “Kids want the emotional relationship stuff and the negotiating skills - how to say no to someone who says ‘if you loved me you'd sleep with me'.”

She acknowledges another sobering stat: the Kinsey Institute says that contemporary women have less sex than their 1950s counterparts because they have so little uncommitted time. Sex has become yet another pressure for busy couples, along with the notion that to have good sex you need a perfect body. It's enough to make you feel nostalgic about the hippy pair in the original Joy of Sex, whose bodies were comfortingly average. Quilliam thinks that the bright young things in the new, in-your-face photographs are equally reassuring, but they look pretty perfect to me.

Yet Quilliam recognises that sex is just as anxious-making as it was pre-Comfort. “I'm glad I'm not ten years younger because there are an awful lot of pressures on young people: to look fabulous; to have a fabulous sex life,” she says. “We're living in a world where it's important to achieve and whether we have a good sex life has become one of our measures of personal validity. Alex Comfort took the emphasis off achievement - that is one of the many things he got right.”

The New Joy of Sex by Alex Comfort and Susan Quilliam (Mitchell Beazley, £18.99) is available from Times Books First for £17.09, incl p&p. Phone 0870 1608080 or visit timesonline.co.uk/booksfirst to go directly to this book, click here.

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