A friend of a friend got talking to a woman at a party. He thought she was attractive and good company and bright. They got on so well, in fact, that he lost track of the time and missed his last train home, so she invited him back to her home for coffee and conviviality and whatever else. He jumped at the chance. On reaching her flat, she disappeared into the kitchen to make drinks, and he started absentmindedly checking out the contents of her living room, at which point he discovered that her bookshelves were monopolised by upwards of 50 titles from the self-help genre. I'm OK - You're OK. Feel The Fear and Do It Anyway. Men Are From Mars, Women Are From Venus. The Road Less Travelled. Women Who Love Too Much. Chicken Soup for the Soul. A Course in Miracles. Etcetera. He looked at the books for a millisecond and drew what he insists was the obvious conclusion. He was trapped in the home of a nutter.

'Alarm bells started ringing,' he says. 'I knew that only bad things could come of this. I felt dreadfully sorry for her, but I knew that I must leave immediately. I told her that staying over on the first night wasn't a gentlemanly thing to do, and I called a cab, which was, in the end, the most extortionate cab ride of my life. But it was still worth it.'

This is how the self-help publishing phenomenon divides the nation. Either you do, in which case, you really, really do (statistics suggest that even the most standard issue self-help disciple owns an average of 12 help books); or you don't, in which case you are perpetually backing away from friends who offer up dog-eared copies of Deepak Chopra or M Scott Peck, with feverish glints in their eyes, promising 'It'll change your life, like it did mine.'

But even if you don't do self-help it is impossible to deny the power of the genre. The self-help publishing industry is directing the way we think, feel and act. Even if we don't buy into it directly, those we date, work with, socialise with, live with and/or share blood with probably do.The gender divide on those buying self-help books is not as pronounced as one might think: 66 per cent of the books are bought by women, 34 per cent by men, while recent researchers into the demographics of the market surveyed an age range of 12- to 74-year-olds.

Over the past 12 months, sales of self-help books generated £38m. The year before that, they made £33m; the year before that, £30m. Occasionally they dominate the bestseller lists (Dr Atkins New Diet Revolution), but usually they sell on a slow- burn, money-snaring, culture-permeating basis. They form, according to publishing trade researchers Book Marketing Ltd, one of the very few publishing genres to experience growth over the past couple of years, at a time when sales of everything else have either plateaued or dropped. But then, maybe the cultural omnipresence of self-help should not be entirely surprising. This is, after all, a nebulous, sprawling genre, embracing everything from survive depression manuals to dating etiquette; from beginner's guides to aromatherapy to quit smoking books.

Dr Nicholas Emler, a psychologist based at the University of Surrey, whose research into the area of self-esteem led him to brush up quite forcefully against elements of the self-help industry, calls it 'the snake oil of psychology'. In his recently published book Therapy Culture, Frank Furedi identifies the phenomenon as part of a greater conspiracy to control us with our reliance on therapy. But millions of other people think that self-help, or at least aspects of it, has changed, even saved, their lives. 'I was in a very dark place indeed,' says Deepak Chopra disciple Chris, 42. 'Did the book stop me killing myself? I don't know. I look at it now and I think it's a bit silly, really. But at that time, it certainly felt very, very important.'

Self-help books have been kicking around in some form or other since Samuel Smiles published Self-Help, a collection of mini-biographies of the great and inspiring - and therefore appropriately life-guiding - in 1859. But if one woman is responsible for the sprawling shape, overall sensibility and power of the contemporary market, it's Eileen Campbell. This is her publishing vision realised. Campbell is a self-help pioneer, although she wouldn't admit to it, principally because 'I think the label "self-help" is patronising,' she says. 'Personally, I prefer mind, body, spirit.'

Most famous for her lengthy, intensely influential stint as managing director of Thorsons, the UK's mightiest self-help publishing imprint, Campbell began commissioning books 'that were probably mostly concerned with spirituality and witchcraft at that time' after she returned, thoroughly enlightened, from a tour of the then relatively uncharted hippy trail in the mid-70s. Over the course of 25 years, with multi-million sellers like A Course in Miracles, Men Are From Mars, Women Are From Venus and The Hay Diet, Campbell masterminded the evolution of what was once called New Age or Alternative publishing into the dominating, mainstream force which she has ensured the industry now refers to as MBS. 'I started doing it because I really did believe that these books could change people. It was a passion rather than a commercial instinct that was driving me,' she says.

By the early 90s, Campbell realised that passion had become a serious money-spinning concern, partly because of the success of what she calls the Shirley MacLaine factor. (In the late 80s, actress Shirley MacLaine became one of the breakthrough stars of the self-help scene when she published a number of books on 'inspiration and truth'.) Campbell discovered she'd inadvertently created a whole new MBS subsection: how to be a phenomenally powerful business creature without compromising your integrity. In this and other ways, her professional progression was matched by a personal one. A great deal of residual darkness and angst has given way to a lighter world view, precisely because she has experimented with many of the disciplines and employed many of the mini-philosophies that her books promote. She has done 'a lot of private study, a lot of meditation, and I think I've got some balance in my life. Really knowing who you are, that's how you become happy. Deep down, most people, basically, want to be happy. But they pursue it in very odd ways. Going deeper, that's how you become happy.' She's dealt with annual budgets of millions of pounds, yet Campbell talks in slightly opaque and whimsical - rather than hard-nosed business - terms.

She believes, wholeheartedly, in the things she publishes (a few of which she has written herself) - she doesn't think she could have done it otherwise. And she believes she's succeeded because society is lacking something that these books, at least in part, provide. 'People might read a book,' she says, 'and it won't necessarily change their life, but it will then make them want to go deeper.

I think with the kind of crisis we're in, the kind of spiritual vacuum we're in - we've got the decay of the church and established religion, we've got no respect now for institutions as such, and people don't really know where to turn - they feel they've got to do it on their own.' Danuta Kean, contributing editor to industry publication The Bookseller, Eileen Campbell and even Nicholas Emler all refer to the demise in the currency of organised religion and of what Emler calls the 'atomisation of society' as essential to the growth in the market.

'I desperately needed someone to tell me what the hell to do when things were difficult in my marriage,' says Kate, 36. 'Therapy wasn't telling me. My friends weren't. It was somewhere else to turn, another option, which actually offered answers, even if they were bogus.' She devoured one of Campbell's titles, Men Are From Mars, found it incredibly insightful, revealing and moving at the time, and then felt that it was misleading, even sexist, the moment she finished it. 'But still, it provided a different way of thinking, and that in itself was useful.'

Sue, 45, was more impressed by Men Are From Mars, which figures large among the seven or eight self-help books she now swears by. 'I had been through a very difficult break-up, the second in the course of five years,' she says. 'After the first split I had been to therapy, where I talked endlessly about my parents, but didn't feel like I got any answers. And it made me feel like being a patient. But self-help books didn't. They made me feel like I was taking responsibility for myself, but being supported. I could go at my own pace. I could take certain elements and dismiss others, while I'd felt that my therapist thought I was failing if I didn't embrace everything she offered. There's a lot of rubbish out there, certainly, but there's a lot of good stuff. I shopped around for the things that resonated with me, and discarded the rest.'

'People are vulnerable to these messages because they're disconnected from traditional anchoring,' says Emler. 'Even if parents and grandparents are around us, life changes at such a rapid pace now that their experiences are completely different, and their advice isn't necessarily valid.'

Compounding this emotional rudderlessness is a violent and completely unrealistic increase in expectations. 'It's funny that we live in a society that talks about freedom, but is extraordinarily proscriptive,' says Kean. 'You have to be happy, you have to be successful, there's no room for contentment or acceptance. You have to be beautiful, you have to be thin. You have to be really good at your job, especially women, who are not only having to redefine themselves in the workplace, but are having to redefine themselves at home.'

Dorothy Rowe is a psychologist, author of 48 books on surviving depression, fear and families, and the sceptic's self-helper of choice, because she adheres to the notion that she can't tell you how to be happy - only, if you're lucky, how to survive. Rowe believes that the very nature of these books means that they can create additional demand for the product, by identifying and making us aware of our ever-increasing deficiencies. She claims that some self-help titles are concerned with creating issues, so that they can solve them - the cellulite of psychology. 'Take something like Women Who Love Too Much,' she says. 'It's made into some kind of mental disorder, when really, isn't this the issue that faces everyone? How much should you look after your partner, and how much should you look after yourself? We all have that, all of our lives. How much time should I spend looking after my children? And 10 years later, it's how much time should I spend looking after my elderly parents? We are creating guilt, fear and problems with these books.'

Yet Campbell insists that forces more elusive than the fleeting whims of authors and publishers control the market. 'There is a straightforward fashion element to the demand for certain topics, whether we like it or not,' she insists. Kean agrees. Self-help catastrophes have almost bankrupted certain publishing houses, she says. An untimely over-subscription to feng shui nearly destroyed one entire imprint. And now? 'Apparently,' she reveals, 'the market on angels - you know, on the idea that you all have your own personal guiding angel - has peaked. It's all about the goddess now, the feminine, about recognising the inner goddess in all of us, and also the one single goddess we should all be worshipping.'

Many different people are writing these books, from the highly qualified psychologist, to the TV presenter, to the journalist, commissioned to produce a book on whatever a certain publishing house believes will be the next hot subject, to people like, well, swimmer Duncan Goodhew, inexplicably. 'It helps if they're qualified, of course,' says Campbell. 'But they need to have a new idea, or a new voice. Also, if they have a particularly unusual or inspiring personal story, that's great. And if they've got charisma...'

Rowe, on the other hand, identifies a distinct psychological profile, shared particularly by the more charismatic, more successful writers. 'It's very tempting to become a guru, because it's power,' she says. 'And as we all know, power corrupts. I've seen this with various gurus I've encountered. They'll start off with a pretty simple message, but they have charisma, and they're good at getting people interested. And often, all they're doing is restating wisdom that has been known by human beings for as long as we've been around.

A lot of it is repackaging.'

Dr Susan Jeffers, soft-spoken and revered author of definitive early 80s self-help book, the phenomenally successful Feel The Fear and Do It Anyway, and over 100 others, partly agrees with the repackaging notion, but doesn't think this is necessarily a bad thing. 'So much of this is learnt by repetition,' she says. 'You need to hear this stuff over and over and over again, in different contexts, using different language. It's about putting a different twist to it all.'

Jeffers doesn't think of herself as a guru, either. 'Well, if you define guru as teacher, yes - I believe that my purpose in life is to learn, and then to teach what I've learnt. If you define guru as anything divine, then no.' She does, however, think that her first book, at least, was something 'that I was divinely driven in, almost'. Feel The Fear happened because Jeffers, who at the time was practising intuitive behaviour, was inspired by a random impulse to present herself at the human resources department of a psychology faculty she had never previously heard of, where she announced to the head of faculty that she had 'come to teach the course on fear'. She was hired, because the department had been looking for a tutor in precisely such a course, and the lessons she taught ('which I pretty much made up as I went along, because they had little to do with the psychology I had studied') became the basis for her multi-million selling first book. 'I will literally go through it now,' she says, 'and think, "What is it about this book? What is in here?" And I don't know. But something in it is touching people.' And is that what makes a good self-help book? 'I haven't a clue what makes a good self-help book. I can tell you what makes a bad one: someone who does not teach about becoming the best of who we are.'

Sue thinks she knows what makes a valid self-help book. 'Quite often those written by very qualified authors, who aren't necessarily advocates of their discipline, who are maybe critical of elements of it, come up with a lot of the wisest stuff. People like Dorothy Rowe.' Rowe believes the good ones 'offer some kind of insight into the self, and some tools for coping. Quick fixes, simple solutions, they're bad news, because there aren't any.'

Next year promises further impressive growth in the market. Incoming trends in mind, body and spirit publishing are predictably varied, and a good benchmark of our ever-morphing angsts. In February, Little, Brown will publish The Program, which, according to the fast-building hype, will be the biggest and most contentious thing to happen to dating manuals since The Rules.

Alongside the Goddess revival, Danuta Kean predicts a major move towards interest in psychic powers and mediums. 'Apparently,' she says, 'anything that the Living Channel is endorsing heavily is a very good indicator of forthcoming trends in self-help.' The ageing baby-boomers are investing heavily in books that prepare them for old age, to guard against failing mental faculties. And for the younger demographic of readers, teenagers and early twentysomethings, the trend in Wicca persists, fuelled, Kean suspects, by Philip Pullman, Harry Potter, Sabrina, The Teenage Witch and Buffy.

No one, apart from Professor Emler, predicts that the mind, body and spirit publishing scene will ever falter. In the meantime, Eileen Campbell will certainly keep publishing her books, in her current incarnation as a consultant to several of the major publishing houses, and will keep believing in them. 'Even if I do have to call it "self-help",' she says, 'is that a bad notion - the idea that we can help ourselves, take responsibility for feeling better about ourselves?' As for Susan Jeffers: 'I love writing,' she says. 'I simply can't imagine I'd ever stop. And I trust my readers to know what works for them and ignore the stuff that doesn't.'