Whit, Iain Banks' latest mainstream novel, is told in the voice of Isis Whit, a young but important member of a small, quirky cult in Scotland. Like all of Banks' characters, from Frank Cauldhame in The Wasp Factory to Prentice McHoan in The Crow Road, she's a character in a half-unconscious search for knowledge which will inevitably turn her world upside down.

Isis, otherwise The Blessed Very Reverend Gaia-Marie Isis Saraswati Minerva Mirza Whit of Luskentyre, Beloved Elect of God III, is granddaughter and spiritual heir of Salvador Whit, patriarch of the Luskentyrians.

The head of the cult must be someone born on February 29. In order to make this more likely a Festival of Love is always held nine months in advance of the date. But Isis' beautiful cousin Morag, the planned guest of honor, has gone missing, and Isis is sent on a holy mission through the incomprehensible world of southern England to find her.

Luskentyrians live in a low-tech commune and reject most technology, even at great inconvenience to themselves. They also run their lives according to a makeshift collection of beliefs and obsessive little rituals which Isis begins by describing with naive earnestness. The heart of the novel intercuts Isis' voyage through southern England, dealing with rastas, policemen, racist skinheads and other dubious characters of a sort she has never encountered, with her recitation of the official history of the cult and the rationale behind its rules.

Banks has two notable strengths as a writer: an ability to speak confidently in the voice of his main character and a penchant for the piling-on of details. He calls on both of these in Whit and does it so deftly that you're carried along in spite of the slackness of the story. What should've been a harrowing tale of worldly perils turns into a rambling, episodic mess with no suspense. The counterpoint between Isis' physical adventure through England and her emotional adventure as she begins to piece together the real history of Salvador Whit and the true origins of her cult feels arbitrary and choppy rather than like an inevitable convergence of knowledge and fate.

Nonetheless, the confidence of Isis' storytelling and the fascination of the details of the cult's origins maintains interest in how the tale will work itself out. Banks also adds some fun with other character voices with Isis' semi-articulate half-brother Zebediah, who only speaks in sentence fragments, and with her Texan grandmother Yolanda, who is entirely convincing and never makes a dialect error that I could detect.

The story falls into two parts chronologically: Isis' quest, and her return and decision what to do with the knowledge she has gained about the discreditable origins of the Luskentyrians. Here again Banks slips from his customary skill. For example, after Isis pursues Morag fruitlessly for weeks, piqued by cryptic messages that her cousin doesn't want to see her and wishes she'd stay away, Morag turns out to be an empty, vapid character passively willing to aid Isis' cause. Isis also encounters other ex-cult members, none of whom pose any sort of danger or create any obstacle, all of whom knowingly or unknowingly provide her with further data that might allow her to discredit her grandfather and possibly dismantle the cult.

Banks conjures up a little tension over Isis' reception by her fellow cult-members and her eventual resolution of the power struggle between her, her brother and her grandfather for control of the cult -- but it's too little, too late. He loses us via the aimless storytelling and also via the essential coldness of Isis' character. He clues us into that early -- "My name is Isis. I am usually called Is" -- and he keeps her very consistent, but she turns out to be one of the least interesting of his main characters by the end.