The Stranger in the Mirror: A Memoir of Middle Age, By Jane Shilling

I felt like a soft-boiled egg, a dissected frog, a jellied blob of sea anemone pecked by the cruel beaks of seabirds": Jane Shilling's memoir is an exuberant epitaph on youth, a girlie chat, an album of memories and reflections on identity, memory, the ageing female body and that other woman over there in the mirror who is not myself. Just cannot be. And is. Je est un autre. The book is a lovely, easy read: Shilling's style, dashingly cavalier and artfully artless, bubbles with wit and brio. Never was a lament less lugubrious.

Like the self, memory is unstable; it flows and changes, dissolving and reforming at every turn. Shilling recreates a medley of crucial moments in a roving present tense. The opening scene sees Jane (17) sitting in a sunny garden with her mother (42) and grandmother (71): they are podding peas and asking one another, "How old do you think you are?" Mum feels 27; Gran 35. Jane is sure of her own immunity to the spell that transformed her mum from a golden, leggy lass into a woman with varicose veins, toenails ridged like limpet shells. Yet here, in a trice, is Jane at 50. There's a crone in the mirror. It's me, allegedly. However did this happen?

The narrator-heroine of The Stranger in the Mirror inhabits a preposterous nursery-tale world, at the mercy of swooping metamorphoses and transformations. Ovidian ironies reign. As a child Jane would awaken surprised that she had not been "turned into a mouse or seal or swan" but was still here, in the same bed. But now look at her – soft-boiled-egged, dissected, jellied, stranded in middle age. She's equipped with a saving joie d'écrire, fighting change with ruefully comic metamorphosis. The Doppelgänger performs curative comic turns in a hall of mirrors. When Jane buys a horse, she has "inadvertently purchased myself in equine form". The child is always evident in the woman – "At fifty, I feel that I am still working out what I want to be when I grow up".

Middle age is by tradition a period of wisdom and creativity. Dante certainly found it so: "Upon the journey of our life midway," he opens his Inferno, "I came unto myself in a dark wood". It is a time for vatic wisdom and creative achievement; for freedom from the impulses and vanities of youth. Shilling does not find it so. She distinguishes rigidly between male and female experience, as if we belonged to different species. But can't I emulate Dante? Do I have to spend my life like the medieval Lady Vanity, gawping at my face in a mirror and seeing a memento mori or a parti-coloured fool? Shilling's story is in part a case history of fatal entrapment by a narcissistic magazine culture.

Yet The Stranger in the Mirror is intelligent and thoughtful, a quest for and valedictory to a self that can never be snared, claimed, construed; it wears its learning lightly. Shilling leafs through Montaigne, George Eliot, Virginia Woolf, Chaucer. The feisty Wife of Bath is celebrated for her farewell to beauty and sexiness: "Lat-go, fare-wel, the devel go therwith!" Good idea – and then, like George Eliot, we might happily devote more time looking out of the window than into the mirror.

Stevie Davies's latest novel is 'Into Suez' (Parthian)