By Rebecca Thomas BBC News Online entertainment staff

If you are the kind of reader who buys a book based on first page impressions, Carol Shields's Unless is likely to be consigned to your pile of great dust-gatherers of all time.

A piece of literature that begins as depressingly as Unless with the words: "It happens that I am going through a period of great unhappiness and loss just now," is hardly screaming to be read.

But the name with which Shields has christened her work, with its all-embracing sense of possibility, should act as a firm guidance when approaching her book.

Adopt an attitude of patience and objectivity and between the covers you will unlock an intelligent, moving, if not wholly satisfying, work of prose fiction.

The book becomes increasing stimulating as it progresses

The voice of desolation at the start of Unless is that of Canadian wife, mother and writer Reta Winters, who is our narrator and sole point of reference throughout.

Unless is not so much a story but a journey into the innermost crevices of Reta's over-active mind.

As a memoir in the most opaque form of the genre, Unless's other characters populate Reta's world but are so sketchily described as to be mere ghosts on the page.

This is true even of Reta's daughter Norah, who Reta would have us believe is the reason for committing pen to paper.

Everything was cosy and ordered in Reta's life until Norah, the eldest of her three beautiful daughters decided to go off the rails.

Reta had a moderately successful career as a translator and novelist, a happy marriage and lovely home.

But then everything was thrown off balance when Norah took it into her head to drop out of university, and life.

Norah's condition sparks the theme that holds Unless together, namely that of woman's subjugation

Now sitting on a street corner in Toronto she begs in a virtually catatonic state with a sign proclaiming "Goodness" around her neck.

The effect on Reta is to prompt her to deliberate upon not just Norah's motives, but every minute incident that occurs in her life.

And this is where one suspects that the true underlying reason for Reta's - or should one say Shields's - formation of Unless is her obsession with words.

Reta admits to loving language, and as a writer this should come as no surprise.

More tellingly, she also says she reads voraciously in order to block out the deafening and continuous dialogue going on her head.

But this is little more than a bluff, since it becomes quickly apparent that Reta's anecdote for her zealous thought processes is writing.

Norah's condition sparks the theme that holds Unless together, namely that of woman's subjugation.

Unconventional

Norah, the writer suspects, has dropped out because she has realised that as a woman it is futile to try to be anything more than passive and unthinking.

This argument becomes increasingly more urgent as the pages of Unless progress, manifesting itself outside the author's own psyche as a number of letters to eminent writers guilty of ignoring women's intellectual contribution to the world.

But this discussion is entered into sporadically while couched in a multi-layered text of digressions from the present, made up of reminiscences, pearls of small detail and general conjectures about life.

The effect of this continuous straying from a conventional line of narration is disorientating, like being in a vast unruly debating chamber where voices and ideas come at you from all sides.

Yet, by the same token, Shields's work also becomes increasingly stimulating as her rich and varied thought patterns touch upon so many of our own.

And if the tone of Unless begins morosely, this is not how it goes on. True, Reta is sad and troubled but the voice she adopts is more elegiac than desperate, filled with love and a gentle desire to understand the intricate fabric of life.

Inevitably such an exercise is futile and as such there is no happy knot-tying at the end of Unless. It is therefore up to the reader to come away from it either deeply irritated or emotionally and intellectually enriched.

Unless is published by Fourth Estate.