The central metaphor in Dorris Heffron's A Shark in the House (Key Porter, 296 pages, $19.95 paper) is teeth: dentistry, tooth extraction and decay, the murderous teeth of sharks.

Holly Kowalski is a middle-aged widow, materialistic, obsessed with her Jag, in many ways superficial. She is a dentist with an inferiority complex, in awe of writers, whose profession she considers much more important than her own. And so she decides to write the story of her life, to probe it as if it were a mouth. But she wants to reach beyond the personal, to include the story of her best friend, Chickadee Lang (who is, ironically, a biographer). She wants to write the story "of us, in our times."

The book opens and closes with the Oka crisis of 1990 but chronicles Holly's and Chick's lives throughout the fifties, sixties, seventies, and eighties, each decade bringing with it its own style, its own crises. Heffron attempts to fuse politics, history, and social commentary with the Toronto setting (the city as reflection of the changing times) and an examination of personal relationships with spouses, children, friends. As if this weren't a big enough bite to chew, she throws in various segments about the Canadian literary scene: lots of name-dropping and obsequious remarks about various Canadian authors, which come across as nothing but self-indulgent fawning.

The pivotal event in the narrative is a shooting tragedy that occurs halfway through the story, which is unfortunate from a structural point of view. Too much of what happens afterward is dénouement, and the shifts in tone-from the after-shock of a murder to a Barry Callaghan party, complete with his father Morley holding court by the fireplace-are disconcerting. It's as if Heffron couldn't quite decide what she wanted to focus on, and as a result the book's seams become all too visible.

The overall effect is of an author trying too hard to imbue a story with significance. Although there are a number of finely crafted individual scenes, the whole doesn't quite work.