Alice Sebold is a master of openings. Who can forget the beginning of The Lovely Bones: ‘After I was dead, I thought about how there had been the light scent of cologne in the air…’. And now: ‘After all is said and done, killing my mother came easily.’ It’s not mere sensationalism: The Lovely Bones was a rich and touching novel, which deserved its huge success. The Almost Moon is even more shocking, and its publishers will hope to make a packet out of it. But that is not Sebold’s fault. What she hopes, I imagine, is what all true writers hope: to stir us to deeper thought and feeling about the tragedy of life – or in her case, as in Conrad’s, the horror.

Helen, our narrator, spends her working life stripping naked for a life class, which neatly conveys her intention: to strip away all covering and reveal the naked truth. As she says when she decides to kill her mother: ‘Shit is shit and truth is truth.’ It would have been even more accurate to say ‘Shit is truth and truth is shit.’ As her ex-husband Jake recalls, ‘You hated everything.’ The Almost Moon tells us why.

Helen’s family story is close to that of Sebold’s own in Lucky, the memoir of her rape (at least we’re spared a rape in The Almost Moon). Her mother Clair is a beauty, a lingerie model (success must be mocked in Sebold’s world) from Knoxville, Tennessee. She marries Daniel Knightly, who is, she believes, ‘in the fashion industry’, but turns out to be a water inspector. They move together to Phoenixville, Pennsylvania, which so far from being fashionable is drearier than East Germany, full of steelworkers losing their jobs. Before long Clair is hurling the remnants of her lost life – paperweights, picture frames – at Daniel, who (again symbolically) ducks gracefully.

In Helen’s earliest childhood her mother is still capable of love, and some pretence of normalcy. But when her looks go the way of her hopes, she descends into permanent panic. By the time Helen is eleven, her mother can’t leave their garden; a few years later she can no longer leave the house, unless Daniel wraps her from head to toe in blankets. When Helen is sixteen a child is run over and killed just outside their front door, but her mother cannot go to him; Helen has to face the crowd of angry neighbours herself, because Clair is incapable. On ‘hard days’ she rubs her chest raw, trying to calm her fear (like Sebold’s own mother in Lucky); on the hardest days she rubs a bloody cavity from throat to breastbone.

Clair is beautiful, witty (though we don’t see much of this), snobbish and cruel (we see plenty of that); but her power comes above all from her insatiable need. Into the pit of this need first her husband and then her daughter fall. Daniel devotes his life to her, and loves her best when she is maddest, the shell of her malice broken. Helen has always both loved and hated her, longed but failed to escape from her. When her own marriage to Jake breaks down she moves back near her; and when Daniel dies, Helen takes over her care, as the greatest posthumous gift she can give him. More than two decades pass, during which her daughters grow up, and Clair adds dementia to madness. Helen spares herself nothing, changing her mother’s nappies ‘like a giant baby’, giving her enemas. Until we reach the present, and page one: Clair shitting herself in her chair, Helen knowing that her life is over, dragging her out on the porch in her blankets and smothering her.

Told in this order, the shock, or anyway the surprise, is less – anyone would want to murder Clair Knightly, especially in her demented dotage. (You may not want to read this story if you are caring for an Alzheimer’s parent: it will bring you up against your darkest self.) But that is one of the best things in the book: the anguished battle in Helen between love and hate for her mother; and the equal battle in us, therefore, between horror and understanding for what she has done. Whenever we hear (and it’s often) that she has dreamt since childhood of murdering her mother, we feel uneasy; when she weeps, and finds she can’t actually cut her up, we’re relieved (though she hacks off her braid instead, which is pretty spooky too). Most of all, she wants her mother to be sane, and knows she is suffering. That we understand. There is something true in what she says, murdering her mother: ‘At least I care.’ And in the end we probably believe her that she didn’t do it out of revenge, but because, when she knew her mother was dying, it seemed the right thing to do. Perhaps we even half think (as she only half thinks) that it’s true.

All this is good, and alas timely: death, like birth, is becoming more a matter of choice every day, and euthanasia is something we all have to think about. The rendering of Helen’s state of mind is good too – the alternation of grief and relief, confession and cover-up; the derailment of all her behaviour once she has committed the ultimate act (‘I didn’t know who I was any more or what I was capable of’). The suspense works – will she be caught? Will her daughters forgive her? Will she disappear, kill herself, turn herself in? But best of all is something else, or rather someone else, entirely: her father. He has always been his daughter’s rock, her only reliable love; even in his own mysterious absences, it was her mother she worried about. That was true in Lucky, too; but here Helen (and the reader) learn something very different. Is this autobiographical too? We inevitably wonder.

For Helen, as she says herself, is her mother’s daughter – as sealed off from the world as Clair, as fearful of life, as marooned in lonely superiority. And The Almost Moon’s vision of the world is as deep-dyed as Helen’s. Daniel – this is the novel’s revelation – is as mad as Clair, indeed madder, filling the drowned house of his childhood with plywood cut-outs of his parents, and finally blowing his brains out in the prison of his home. Most parents are ghastly, most children die horribly. Helen’s idlest thoughts are appalling – thinking of sliding down a banister, she sees her head split open and her mother stomping around in her brains; seeing the wire support around a sapling, she wonders ‘if anyone would remember to cut it off before the tree slowly strangled’. The sex is graphic and faintly perverse (Helen even feels a surge of lust lifting her mother’s wrinkled dug); no physical detail is spared, from Clair’s rectal examination to the faecal reek of her last hours, and the snapping of her nose as Helen presses down too hard on the towels.

Everything is sick, distasteful, horrible. So in the end, like Jake, you dissent. Instead of awakening you to tragedy as The Lovely Bones does, as all good writing does, The Almost Moon makes you want to keep your eyes firmly closed.