BOOK REVIEW / The minister for sins: 'Dunedin' - Shena Mackay: Heinemann, 14.99

THAT A NOVEL packed with as many fine things as Dunedin can still feel like a missed opportunity is testament to a copious but careless talent. Brilliant details go skittering by, the reader catches their glint, and meanwhile a narrative rolls indifferently on. There are virtuoso sentences, oven-fresh imagery, a sense of great verbal tact; so why should the book housing them be, for much of its stretch, quite so uncompelling?

Certainly the first 50 pages put on a glorious opening stand. Set in turn-of-the-century New Zealand, these concern the arrival in Dunedin of the Scottish minister Jack Mackenzie and his family. A cleric by profession, a naturalist by inclination, Jack is 'at his nicest when being botanical'. At his worst, which is the rest of the time, he neglects his forlorn, homesick wife, Louisa, bullies his young son, Sandy, and lusts after the dusky laundress, Myrtille, a proud Maori who keeps the head of her great- grandfather on the mantelpiece.

Shena Mackay sketches this remote, God-fearing community with an exactness and economy that leave you baffled with admiration. Minor characters, such as the housemaids, Madge and Lilian, or the prim parish busybody, Miss Kettle, are first registered from the corner of an eye; then some glancing detail, casually appended, gives them lives of their own. They suggest a richness and eccentricity that could fill a whole sequence.

Just when the book seems beautifully poised, the narrative takes a wrong turn. We are catapulted 80 years on to contemporary London and the miserable menage of Olive Mackenzie and her brother, William, grandchildren of Jack the pastor. Their story constitutes the bulk of Dunedin. Olive, 'a bitter fruit with a hard stone at its heart', is a wretched sack of nerves, bruised by her marriage (a write-off) and a recent affair. Similarly adrift in middle age, William is a disgraced former headmaster, stricken by the memory of a pupil killed in his charge.

There is drama of a sort. In one of her more deranged moments Olive goes baby-snatching on the Tube, then undergoes an agony of loss and the fear of discovery. A poignant but not very interesting sub-plot follows the downward spiral of Jay Pascal, a waif from New Zealand and descendant of Jack Mackenzie's fateful liaison with Myrtille; fetching up in south London's squatterland, he is eventually arrested and packed off to a sinister prison for unwanted flotsam and jetsam.

The story maunders on, enlivened by passing details of colour or sound. Somehow, 'ink which had rusted to the colour of old thin blood' is eerily right, so, too, the 'dingy whiteness of the launderette'. And there is something piercingly sad in Mackay's alertness to the banal, as when Terry Turner, a literary London shit, recalls the moment when his affair with Olive began to crumble: 'Terry and Olive had been sitting side by side watching television and eating corn chips with a taco dip when he had become aware of a cracking in his ears. The sound of crunched crisps was the sound of falling out of love.'

Mackay's great gift is similar to Penelope Fitzgerald's, a matter of giving odd twists to the ordinary yarn. Olive and her girlfriends sit around hankering for their mothers' generation, a happier time when they had 'lovely kitchen cabinets in lemon and eau-de-nil and Goblin vacuum cleaners and the kind of gas you could kill yourself with'.

It seems ungrateful to carp in the face of these felicities, yet one feels decidedly short-changed. The majestic fluency of the New Zealand prologue holds out a promise that the main narrative slowly fritters away. The writing is a thing of beauty, but the rhythm of the book slumps alarmingly, a crabbed scuttle through the sleaze and heartbreak of south-east London. There's another glimpse of what might have been in the epilogue, which transports us back to Dunedin and the disclosure of Jack Mackenzie's wrongdoing: 'They were moving across the grass towards him, grave and black as vultures against the green, a convocation of elders.'

The rest is history - the history that Dunedin could have been.