Some authors like to beckon us in with a quiet smile, leading us up the garden path and saving a few surprises for later. Alice Sebold is not a novelist of this sort. She prefers to kick her way in. Her new novel, “The Almost Moon” (Little Brown, 204 pages, $24.99), the keenly awaited successor to “The Lovely Bones,” opens, like its predecessor, with a sentence arresting enough for the publisher to spread it across the back cover as a shout line. “When all is said and done,” it goes, “killing my mother came easily.”

It is a striking gambit, which has already attracted equal measures of admiration and dismay. It certainly snapped this reviewer’s eyes open, and the succeeding pages, in which the heroine cleans her mother’s dead body in a vivid hallucinogenic daze, have a clean, intense edge. It is evident that the smothering of her mother was neither a demented accident nor a sudden whim, but the fulfilment of a long-suppressed wish. The book traces the history behind this stark deed, and hardly anyone can finger such bruises with as much precision and vitality as Ms. Sebold. Familiar objects — chairs, locks of hair, picture frames, blankets, nail polish, and apples — quiver with life.

She specializes, too, in extremes of candor that have the force of confessions. “My mother’s core was rotten,” she writes, “like the brackish water at the bottom of a weeks-old vase of flowers … When I was a teenager, I thought every kid spent sweaty summer afternoons in their bedrooms, daydreaming of cutting their mother up into little pieces and mailing them to parts unknown.”

The gambit almost works. But there are risks attached to opening with such a zinger, and as the novel proceeds it becomes evident that even a writer as gifted and intent as Ms. Sebold cannot evade them.

The first peril is the most obvious: After starting at such a high point, it is almost bound to seem downhill all the way. Later incidents are hardly likely to be so resonant; when the biggest punch is thrown right at the outset, nothing that follows can match it.

The second difficulty is tonal. The line gives us a shake because it is laconic to the point of jaunty. If anything, it suggests black comedy, with its echo of the famous opening to Flann O’Brien’s “At Swim Two Birds” — “Not everybody knows how I killed old Philip Mathers, smashing him in the jaw with a spade.” But Ms. Sebold is not aiming for surreal Irish comedy; on the contrary, she is a spit-in-your-eye realist, famous for working the blurred seam between fiction and memoir. At the very least, the throwaway manner of her first line distances us from the narrator. She doesn’t seem to care, so why should we?

Naturally, Ms. Sebold is not trying to make us “care” on this sentimental level; this is not a romantic saga about mothers and daughters. Indeed, part of its purpose is to dramatize the way in which sour behavior (the narrator’s mother has always been mean and impossible) is a characteristic every bit as heritable as eye and hair color. But this leads us to the most treacherous hazard in that brilliant first line: The most dramatic event has already happened. The approach is poetic: The rest of the book will ride the ripples from this heartbreaking event, but we won’t witness it first-hand. Eleven small words are enough to hobble any real narrative suspense.

Ms. Sebold tries for some urgency toward the end, when her heroine makes a clumsy attempt to bamboozle the police, but if it is crime-novel suspense you are after, then, to be frank, you are better off with John Grisham. And it may be this need to contrive a sense of surprise that sends Ms. Sebold’s heroine straight from her mother’s deathbed and into some cover-your-eyes backseat sex with her best friend’s bewildered son. In one way this fits with the taboo-busting brassiness of the book’s scheme. In another, it is wearily formulaic: It isn’t only in Mills & Boon, evidently, that the heroine must have sex on page 69.

It might strike Ms. Sebold as unliterary, but it is hard not to dream of the novel she could have written had matricide been the climax of the story, rather than the beginning. What a lethal tale it could have been: the daughter of two strange parents fighting their demons; a mother who retreats into erratic fury, a father who commits suicide, a heroine whose own marriage fails and who feels the force of her parents’ madness infecting her own life, the swelling conflict between pity and vengeance … It could have been “The Princess of Tides”; it could have been magnificent.

As it is, “The Almost Moon” is a calm, retrospective survey of a life twisted by the pressure of family obligations. It feels muted, an almost-firework that must have already lit up the sky somewhere else, because it now seems low on sparks. You can still tell that Ms. Sebold is an exceptional stylist; the worldwide success of her first novel was no fluke. But this time, alas, she has bitten off less than she can chew.

Mr. Winder has been an editor at the Independent and Granta.