AS SOMEONE who approached her 50th birthday with the opposite of equanimity, I looked to Germaine Greer's seminal book, The Change, now revised and updated for a contemporary audience, to fill me with positivity. Surely a feminist as provocative and irrepressible as Greer, who is still causing trouble at the age of 79, would show me how to confront ageing and the menopause with defiance and elan. Provided I lived long enough to complete its 436 pages, I expected to emerge re-energised with a renewed sense of purpose.

Unfortunately, The Change turned out to be both frustratingly unfocused and profoundly pessimistic. It starts from the premise that women who reach their half-century are invisible and ends with the prognosis that the best we can hope for is a zen-like acceptance of a post-sexual state. Like an anti-Dylan Thomas, Greer tells us not to bother raging against the dying of the light. And, for God's sake, don't wear purple.

It is true, as Greer points out, that women do not talk enough about ageing and the menopause, even amongst ourselves. There is still a stigma attached to the end of menstruation; a sense that the packing up of our ovaries is an admission that we are spent. Though, for some, symptoms such as hot flushes and night sweats can be debilitating, they are not openly discussed in the way the indignities of pregnancy and labour now are. Giving birth, after all, is proof of fertility; the menopause the end of a woman's reproductive capacity - the standard by which her usefulness has traditionally been defined.

Added to the stigma is a lack of clarity over its onset. The start of both the perimenopause and the menopause are difficult to establish. You cannot be sure if you have had your last period until quite a long time after it has happened and symptoms such as fluctuating mood may also be bound up in other life events, such as your children leaving home, and a general sense that your place in the scheme of things is shifting.

There is a lot, then, for Greer to get stuck into and her approach is refreshing. Refusing to get bogged down in the medical details, she instead explores women's experience through historical references, anthropological works and literature. Along the way, we hear fascinating snippets about the way a range of women have fared after 50: the upbeat tale of the beautiful Diane de Poitiers, loved until death by King Henri II of France despite being 17 years his senior, is counterbalanced by that of writer George Elliot, whose second husband John Cross - 38 to her 58 - apparently jumped out of a window on realising he was expected to consummate the union.

Yet the subject is so large and unwieldy and the book so lacking in structure that it can be difficult to establish exactly what Greer’s saying. For example, she rails against the medicalisation of the “climacteric” - as she prefers to call it - and the (mostly male) Masters of the Menopause who have treated the symptoms with everything from purgatives to sulphuric acid, but her coverage of hormone replacement therapy is contradictory. She casts doubt on the benefits of flooding the body with oestrogen (as HRT does), yet later on quotes Joan Collins describing it as a miracle drug which can “prevent brittle bones, increase energy levels and make dull skin glow again.” She criticises the excessive carrying out of hysterectomies and yet raises fears about the Mirena coil which can stem bleeding and prevent them.

The Change is also undermined by generalisations and unsubstantiated assertions; in one section Greer looks at the way in in which some other cultures mark the transition from youth to middle age. In the Mediterranean, she says, women of a certain age wear black and carry out the duties of mourning by regular visits to the graves of dead relatives. "Passers-by can click their tongues," Greer writes. "The woman herself does not expect them to understand. Her behaviour is proper to her at her time of life and that thought suffices her."

It is impossible to discern any basis for this statement; there are no studies cited, nor is there any suggestion she has interviewed any of these women. How can Greer be sure they do not resent their positions as custodians of plots they will soon be inhabiting?

Underlying much of what Greer writes appears to be a faint distaste for sex, or at least an assumption that marital sex is an obligation most would be all too happy to be relieved of. She talks about post-menopausal women's declining interest in physical relations, almost as if it is a given, yet simultaneously references those like Tippi Hedren and Elizabeth Taylor who never lost their lust for lust. Overall, the problem seems to be that there are as many different ways to react to the menopause as there are women, which makes it difficult to form any coherent argument or narrative thread.

In her final chapter, Serenity and Power, Greer posits the idea that once women have successfully navigated the turbulent waters of the change, they can berth their ship in a safe harbour with an obstruction-free view of clear blue skies. Amongst the many poems she includes is one by Christina Rossetti; it is about a woman, probably her mother, who has overcome the emotional turmoil brought on by ageing, and is one of the saddest things I have read.

"Ten years ago, it seemed impossible

That she should ever grow as calm as this

With self-remembrance in her warmest kiss

And dim dried eyes like an exhausted well," Rossetti writes.

Most of the women Greer eulogises come to rejoice in "the passive state of a looker-on” liberated from the active service of life.

If this is the best she has to offer, I think I’ll leave it. thanks, Perhaps when I'm 90 that kind of lobotomised tranquillity will hold some appeal. Until then: give me the pain and restlessness and melancholic ache of middle age; give me angst and fear and messiness and all those things that are the price of being properly alive.

ends