"Of course there's a difference between men and women," a wily old journalist of my acquaintance used to say. "It's a vas deferens." Non-medical people might be reaching for the biology textbook but the physiological pun always drew a laugh in the jaded sub-editors' room in days of yore. Joan Smith doesn't have the benefit of such wit in her introduction to Different For Girls, the latest extrapolation of the vast difference that divides personkind. But she does have a quote from a sublime eponymous pop song by the British musician Joe Jackson, which, like my friend's joke, dates back to the early 1980s. The irony about this, which she doesn't explore, is that the song Different For Girls was all about standing that difference on its head. It was role-reversal: instead of the boy backing away from love and commitment, as in the social stereotype, it is the girl, horrified at these demands confronting her: "Who said anything about love?"

The book that Ms Smith - author of the earlier, celebrated Misogynies - has written is a welcome if middle-of-the-road addition to accessible literature for women who want to have the same options and opportunities in life as men. Joan Smith says she is not at all bothered by the stridency sometimes associated with the label of feminist and considers herself one of the sisterhood.

She is a fortysomething writer who has remained single and childless by choice, although she points out in the book that she enjoys loving relationships with men. I wondered how much her view of woman's role or roles had been informed by the censure which she had met from both sexes because of her decision, taken very early in life, that she did not want children. Motherhood is such a key image of women - in many societies still the only image, and I'm not only talking about obscure tribes hidden away in the Andes. It could be a street in any town in Ireland.

"I think my decision not to have children is a major clue to the ideas that turned into this book," she says. "I always had an unusually clear sense of what kind of person I wanted to be and I was surprised at the extent to which other people seemed taken aback by this." She points out that through history male adventurers, artists, dons, have often eschewed domestic life and this never raised eyebrows but when a woman such as the mountaineer Allison Hargreaves dies in a climbing accident there is a backlash of blame at the parental "irresponsibility".

Coincidentally, as Different For Girls is published, this week the BBC is broadcasting a three-part series on radio on the growing visibility of women who are childless by choice. Britain's Family Policy Studies Centre is collating research on the trend by which, as one academic said on Radio 4, more women are thinking twice about the "15 to 20 years of house arrest which children entail".

Of course there is a bitter irony in this focus coming in the same week that the loss of Princess Diana, a woman who was defined by two quintessentially "feminine" attributes - motherhood and glamour - is having such an astonishing effect across the world. It was noticeable that in some of the more pompous Establishment commentaries on her death she was still seen as principally the mother of the future sovereign.

The theme of the woman who rejects the role of herself as a vessel, an adjunct, however necessary, to other more active people, is a strong theme through Joan Smith's new book. It sets out to examine the direction in which a woman's place in the world, if that's not too portentous, is going at the end of the 1900s. By far the most interesting section is the final part of the book, Five Propositions And A Conclusion, which traces the background to much of the received wisdom about what women can and can't, should and shouldn't, do or be.

But the earlier parts, although a good read, are somewhat fairy-flossy. There is the inevitable section on Marilyn Monroe, for example, and a chapter devoted to Jacqueline Kennedy Onassis, titled The Last Silent Movie Star. Smith also compares today's supermodels with the women the 19th-century Pre-Raphaelite painters used as models. This is an interesting enough analogy: the inspiration for paintings such as April Love and The Lady of Shalott which hang in London's Tate Gallery were waifs picked up and brought home by the artists, to become "stars".

Claudia Schiffer was a 17-year-old schoolgirl dancing at a discotheque when a French modelling agent spotted her and pursued her until she took him seriously. Now she earns around $12 million a year - but isn't she also largely the passive creation of an exploitative male? Likewise Kate Moss was queuing with her father for airline tickets when her particular appeal was noted - by a man. Smith sees the essence of their appeal as their "ability to offer their perfect - and perfectly blank - faces as a canvas on which all kinds of fantasies can be written".

The popular, populist veneer of Joan Smith's book is understandable when you look at what she's competing with out there on the bookshelves: "know thyself" works such as John Gray's Mars And Venus series (latest: Mars And Venus On A Date). Gray, whose evangelical zeal for sorting out inter-sexual relationships at the end of the millennium has made him a very wealthy man, is about as far from Joan Smith as, say, Mars is from Venus.

He has sold more than five million copies of the first, Men Are From Mars And Women Are From Venus. Intelligent people buy his books. I have seen them run for a copy; and all to be illuminated by tenets such as "A man is attracted to a woman/ Who clearly can be pleased."

Now what does this mean? Search me, but it makes a great little litany to chant as you wheel the trolley around the supermarket - oops, guilty of gender stereotyping! I mean it is a grand litany to chant as you change the oil on the old MG or operate mission control for Mir.

I hope the brave people like Joan Smith who think there is more to being a woman than showing you clearly can be pleased, will not be silenced. Although her book doesn't break any dramatic ground, it is another valuable contribution to the good cause of making everyone realise, to end with another 1980s pop tag - this time from the Au Pairs - that "we're equal but different".

Last week, when I read Joan Smith's book, she was in the same position as hundreds of authors who have analysed, parsed and dissected, minutiae of Princess Diana's behaviour: the princess is the first powerful role model in the book, with a chapter devoted to her. Smith came to the conclusion that Diana had learnt the advantages of being portrayed as a martyr, without taking on the virtual vow of silence that Jackie Kennedy assumed after the great drama in her life.

How could any of us know then, as contemporary women, viewing the beautiful Diana with a critical, half-envious eye, that all too soon she would be dead and actually a martyr in the eyes of millions of those to whom her rich traditional femininity was a glorious, unattainable, gift?

Different For Girls by Joan Smith is published by Chatto & Windus, £10.99 in the UK.