By Margot Livesey
Harper Collins
336 pp., $26.99
Reviewed by Dan DeLuca

The seven letters in the title of Margot Livesey's ninth novel are laid out on the book cover to appear like an eye chart.

Donald, the protagonist and principal narrator who, like Livesey, was born in Scotland and now lives outside Boston, is an ophthalmologist. He's given up surgery but now practices optometry, so "more than most people, I have tested the hypothesis that the eye is the window to the soul."

He's a careful man who thinks his first 10 years spent in Scotland "inoculated me against American optimism." The way he sees it - or used to, before his life was turned upside down - "in my modest fashion, I was contributing to the spread of Scottish values: thrift, industry, integrity."

Mercury is a book about marriage, and blindness: the inability of the sighted to see what's right in front of them. Cautious Donald is married to impulsive Viv, a woman who - guided by her favorite Margaret Fuller quotation: "Men for the sake of getting a living forget to live" - gives up selling mutual funds to join a friend in running a stable.

Livesey's story - told mainly by Donald, and less effectively by Viv - is a love triangle. The title character that enters the couple's lives like quicksilver, however, is not man but beast. Mercury is a horse, a sleek, gray, gifted 5-year-old Thoroughbred housed at the stables.

Mercury rekindles the passion Viv lost when Nutmeg, the horse she rode competitively as a young woman and the only past relationship she felt worthy of mentioning to Donald when the couple were courting, came up lame. The new extraordinary, unquestionably beautiful horse switches on a light in her that died when the death of Donald's father led her husband to retreat into prolonged grief.

Mercury is fast-paced, with the feel of life as lived. The secondary characters are well-drawn, including the couple's two children, caught up in the family drama; Donald's patient-turned-close-friend Jack, who is blind; and his childhood pal Robert, present mostly as a memory. Colorful asides from Nabokov, the talkative parrot of Donald's father, are a winning, whimsical touch, not overplayed.

The middle section of the book, narrated by Viv, is structurally and thematically necessary. We need to hear her version of the events as they take a troubling, near-tragic turn. (In Livesey, as in Chekhov, when a gun turns up in a domestic drama, it's bound to go off.)

Viv's voice helps us understand the limits of what Donald sees and understands about her, just as it explains how she has been blinded by Mercury's light. Livesey never seems as completely invested in her, however, and it's a relief when the story returns to the perspective of our myopic eye doctor, who can see what has happened to his family only after it's too late.