August is the quietest month,' intones manager Malcolm Smith as he folds his giant frame into a chair in the store-room of Karnac, Britain's only specialist psychoanalytic bookshop. Piled to the ceiling are copies of sober psychoanalytic and psychotherapeutic texts such as Andre Haynal's The Technique at Issue and Neville Symington's The Analytic Experience. But Karnac is the scene of more than just the transaction of money for books. Its two branches - on the edges of shrink-land in London's Finchley Road, and Gloucester Road, Kensington - have become centres of pilgrimage for thousands of people bitten by the therapy bug.

'August is when psychoanalysts take their long holiday, and most patients take the chance to go away then too,' explains Mr Smith. 'But in July, if the International Psychoanalytic Association is convening, say in Amsterdam, you'll see many of the most eminent analysts in the world in here, browsing, and of course moving their books to the front of the display.'

What began with Freud 100 years ago now sustains the burgeoning 'helping professions' and permeates thinking on everything from management to probation work. Karnac's customers reflect this diversity. Jewish earth-mothers and callow youths rub shoulders at K for Klein and L for Lacan. The store is also well-known for having a sales staff with a special interest in psychodynamic thinking. Karina Spero, 31, is typical. She has undergone therapy, is considering training as a therapist of some sort, and catches up with the literature in quiet moments. 'The people who come here are very civilised,' she whispers over the studious hush. 'You overhear a lot of therapists talking shop too, which is fascinating.'

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Aside from the rush hours, which partly depend on the timetable of the nearby Tavistock Clinic, both shops always contain a handful of ex- or ongoing patients for whom the 50-minute session with an analyst is not quite enough. Here you can mug up on the latest theories - and the chances of bumping into the supposed object of your desire (your therapist) are even greater than in Waitrose across the road.

Harry Karnac set up shop in Gloucester Road in the late 1940s. Donald Winnicott, Britain's greatest paediatrician, soon became a regular. Mr Karnac approached him one day because he couldn't understand how he got through so many biographies - famous soldiers, scientists, entertainers, he was buying everything. 'Oh, I'm only interested up to the age of five,' replied the child psychoanalyst. It was only when Winnicott suggested that the store ought to stock more mother and baby books, as his patients were constantly asking for recommendations, that Karnac began to specialise in psychoanalytic texts.

In 1984 Cesare Sacerdoti, an eccentric Italian, bought the store and inherited a mailing list of 700 people. Today 22,500 around the world receive the slim white catalogue, and Karnac itself publishes about 25 books a year. It reprinted early texts by Ferenczi and Ernest Jones when the original publishers had given up on them, and even sell American books back to the Americans.

Mr Sacerdoti is a layman. He is not a clinician, nor has he ever been analysed. 'That's one thing that bugs some people,' he laughs. 'I have never been on the couch.' He does however, read all the books which Karnac publishes, and much of the new stock. 'People ask me to recommend books all the time. But when they ask if I can refer them to a good analyst, I say certainly not]'

He has witnessed some growth areas in the last decade. 'I remember in 1985 the only book you could find on the subject of child sexual abuse was a two-volume survey by the Canadian Government. Now it's a whole new section. Also, the practice of family therapy, where you deal with the family as a unit, has become a big new area amongst the book-buying clinicians. And of course books on transference (falling in love with your analyst) always sell well.'

And the 24-volume Standard Edition of the Complete Psychoanalytic Writings of Sigmund Freud, which costs pounds 500 and comes in its own box? 'We sell about 100 sets of those a year, worldwide,' says Sacerdoti. 'Most people settle for the paperbacks, one at a time.' 'The Interpretation of Dreams and the Introductory Lectures sell best,' adds Malcolm. 'Volume 15 is a bit slow, though - Historical and Expository Works. So is Jokes and Their Relation to the Unconscious. It's just not very funny.'

Karnac, 118 Finchley Rd, London NW3 (071-431 1075) and 58 Gloucester Rd London SW7 (071-584 3303)

Best-selling psychotherapeutic texts at Karnac over the last 10 years: 'On Learning From The Patient', Patrick Casement; 'The Language Of Psychoanalysis', Laplanche & Pontalis; 'Melanie Klein Today', essays by Kleinians; 'Individual Psychotherapy and the Science of Psychodynamics', David Malan; 'Impasse and Interpretation', H Rosenfeld; 'Live Company', Anne Alvarez; 'The Patient and The Analyst', Joseph Sandler