"When Polly was a child, and thought like a child, the world was a fluid place," Jamie Harrison's new novel begins. Lately, though, "Polly thought her mind was a river, constantly scouring and pooling, constantly disappearing, filling with details that glinted and vanished." What separates then and now is a head injury in whose wake "the world became terribly fragile; the center, the imperfect brain Polly had been fond of, had fallen apart."

"The Center of Everything" takes place (mostly) in Montana, and yes, a river runs through it — the Yellowstone, beautiful and treacherous; but also more metaphorical waters transporting us through time. Forty-two-year-old Polly — caterer, editor, vetter of scripts, mother of two young children, wife of lawyer/restaurateur Ned — is trying to piece things together again, to distinguish memories from dreams, to remember what happened years ago, yesterday, in the past 10 minutes. And as she tries to fix time, or at least get a fix on it, two events orient her efforts — and the novel's plot. One is a 90th birthday party for her formidable great-aunt Maude, which she is tasked with hosting. The other is the drowning, under possibly suspicious circumstances, of a much-loved young townswoman, Ariel.

The party, gathering multiple generations, unlocks a family history rife with mysteries and secrets; and the drowning, with its echoes in the family's past, brings some of those secrets to the surface. There may be a bit too much consonance between the events past and present that give the novel its structure. But, in light of Polly's great-grandfather's work as a famous excavator of myths, à la Joseph Campbell, we might also see such coincidences as reflections of a larger, more intricate design than the tangled branches of one family tree.

The nature of Papa's work also peoples Polly's story with a wonderful cast of interesting characters: writers, artists, historians and crazies whose erudition, curious ideas and inspired eccentricities infuse Polly's mental mapmaking with shimmering light and color. And it is really the way Polly thinks — about her children and her childhood, her memories and imaginings, her immediate circumstances and her place in the world, even the toothsome dishes she prepares (with occasional lapses lately) — that makes this book so engaging.

"She had always looked too hard at things," she thinks. "Now, though, pictures sometimes scrolled around her even when her eyes were shut — a ribbon of color and random objects, usually beautiful but sometimes terrifying — and if she concentrated on a painting or photograph, she sometimes went inside of it, the way she had as a child. … She felt as if her eyes could enter any surface: the ground, the river, closed curtains, flesh."

Carrying us along, Polly conjures a richly textured, often lovely life of everyday loss and longing and endless speculation, where "everything goes missing but everything lives on, at least for a while, in the small kingdom of your head." Indeed, Harrison's novel takes the unreliable narrator to a whole new place: in short, to the center of everything.

Ellen Akins is the author of four novels and a collection of stories, "World Like a Knife." She also reviews frequently for the Star Tribune.

The Center of Everything

By: Jamie Harrison.
Publisher: Counterpoint, 304 pages, $26.