A feminist critique of this book is easy to make. Websites have sprung up with titles like 'A Rebuttal From Uranus' (Susan Hamson) which argue that Men Are From Mars institutionalises sexism. Sex-role theory, of which Gray is a prime specimen, says that men and women are by nature very different, and that gender forms the core of a person's identity. Gray is particularly insidious, these critics say, because he never presents his views as a theory, simply saying 'this is the way things are' (biological fact). His millions of readers, caught in a marketing blizzard, are blinded to the alternatives and the fact that gender roles are actually culturally conditioned. The ultimate aim of Gray - consciously or not - is to make women feel better about their subordinate place in a hegemonic masculine culture.

Before taking sides, we must first actually read the book. What are some of Gray's main points?

• The golden key to better relationships is the acceptance of differences. In our parents' day, everyone accepted that men and women were different, but the culture changed to the other extreme of there being no differences.
• A woman aims to improve a man, but a man just wants acceptance. Her unsolicited advice is never welcomed; it is interpreted as negative criticism. Rather than presenting a problem to a man, which is often taken to mean he is the problem, a man should be approached as if he may embody the solution. Men are focused on their competence, and if they cannot solve problems, they feel they are wasting their time. Women, on the other hand, actually like to discuss problems even without a solution in sight, because it gives them the all-important chance to express their feelings.
• Women are like waves, rising to peaks and then falling into troughs, then back up again. Men must know that the trough-time is when women need men most. In being supportive, and not trying to get the woman out of the trough immediately, she feels validated. In order to be motivated, a man must feel needed - but a woman must feel cherished.
• Men alternate between the need for intimacy and the need for distance. Men's going away into their 'cave' is not a conscious decision but is instinctive. Women who don't know about the need for the cave and seek constant intimacy will see relationship turmoil. Like a rubber band, a man needs to stretch - but will usually spring back.

The criticism of Gray's worldview may be valid, but on the other hand he wrote the book for an audience of people who do not read genetics or sociology textbooks - they want better relationships now . Men Are From Mars does not advance cutting-edge theories, but neither does it say that men and women are roped to the poles of their sex; we have tendencies to action which, if recognised, need no longer be our master.

By highlighting sex differences, Gray may be guilty in some courts of entrenching patriarchy, but nowhere in his writing does he go so far as saying that gender determines the person. The public would not have touched the book if he did. If the goal of focusing on sex differences is, paradoxically, to move beyond them, then to answer our initial question, Gray is a liberator.

It is very, very easy to dismiss this book. But read it when you are in misery following a fight with your partner, and it may come alive for you. As a simple guide to the ups and downs of living with a member of the opposite sex, it does have touches of brilliance.

Whatever is said about the book, it has been right for its times, and perhaps we needed to be reminded of our differences before we could move beyond them. The finest people, as Emerson noted, are able to marry the two sexes in their one person.