SUSAN Howatch has recently been through a gradual spiritual awakening, which has taken her well beyond her racy phase, when she produced novels like The Rich are Different and Sins of the Fathers. This change is amply reflected in her Starbridge novels, an examination of the Church of England in the 20th century, culminating in this, the sixth volume, Absolute Truths. There will be no more in the series, Howatch has made clear, despite requests to carry on. As she has observed, the final book brings her protagonists - three Church of England priests, each representing a different strand of thought in the church today - to the point where 'everything is redeemed and completed'.

Howatch deserves praise for her stamina in seeing through this massive project. She has unflaggingly sustained her attempt to tackle the quest for a higher spirituality and psychological awareness in the pacy way that some other writers deal with romance. Her vicars lose faith, or at least find it severely shaken, much as characters in traditional romantic fiction lose love or have it sorely tried. Howatch has remained admirably true to her didactic aim.

But it is precisely this quality that is also Howatch's undoing. Absolute Truths is nothing if not didactic, so much so that it doesn't seem to ever really get going. It's the mid-Seventies and the traditional, upright, urbane Charles Ashworth, now-retired Bishop of Starbridge, is looking back over his turbulent years during the previous decade. As the narrator of the first book in the series, he is fittingly the voice of the last. Yet as Ashworth relives his troubles, most notably the death of Lyle, his second and beloved wife, none of it has much impact. It's as if there is something more to come, but it never does. The problems are not made gripping enough - nor, frankly, are any of the characters. Howatch skims over her story as if she is at the helm of a hovercraft that is hurtling headlong, on schedule, to a very specific port. But when she finally deposits her characters there, and they are told several times during a sermon that 'All things work together for good, for them that love God,' it is hard to believe this is supposed to be a deeply satisfying denouement to six volumes of spiritual inquiry.

None of this is helped by the self-consciousness in the writing. Her vicars get 'hot' under their 'clerical collars'; they repeatedly use phrases that hark back to the titles of her previous books in the series, 'glittering images' to describe how they believe they must portray themselves to the world, while noting that they are taking 'scandalous risks' whenever they stray from the righteous path. 'Absolute truths' becomes the buzz phrase in the final chapters to flag that someone is proffering what invariably amounts to disappointingly undigested Christian doctrine. And do all vicars really go around with their tongues hanging out for a Tio Pepe sherry? (There are so many references to the stuff that I would have thought Howatch deserves advertising royalties.) Moreover, when Loretta, an attractive American academic returns on the scene to reclaim Ashworth, with whom in years past she 'rolled in the hay', we are overtly reminded in virtually every reference to her and every word she utters that this is a bold, brassy Yank compared to conservative, classy Charles.

The idea of theological exploration as a literary theme is an excellent one. But perhaps Howatch should turn her creative hand to depicting her own journey from heretic to heartfelt believer. In doing so, she might have a better shot at achieving spiritual profundity.