Five minutes later, the reading is over. Q&As commence and it becomes clear why these appearances might be a little battering for Sebold. "I am curious to know if the story you read has a parallel to your own life?" asks one woman. "Is your mother living and what did she think of The Almost Moon?" asks another.

"Can you tell us about your background?" asks a man, apparently unaware of Lucky. "Did you have siblings, where did you grow up, had you any other ambitions besides writing?" "My weight?"

Sebold tries to joke. "It's visible, " the man shoots back.

The barrage eventually dies down but one presumption remains in the air: that no matter what Alice Sebold writes, there will be a code, a key to it somewhere, buried in her real life or her memoir, if only the public can keep her still long enough to ask about it. And she's not entirely a victim to this assumption. "What did you like to read growing up?" one guest asks, to which Sebold replies, a little too quickly to be fibbing: Sylvia Plath, Robert Lowell, all the confessionalists.

"I knew I made a mistake when I said that, " Sebold tells me two days later from San Francisco, where she moved recently with her husband, the novelist Glen David Gould. Her voice has a husky, deadpan pallor . . . the sound of brutal honesty. Then she catches herself and changes to a more controlled timbre. "Those were the perfect poets for me at the time, living in the suburbs where I was growing up, because they had a certain intelligence and spice which told me where I was living and what I was experiencing was not the whole fabric of the world." The world she would eventually encounter almost need not be explained, so familiar is it from Lucky: the brutal rape, her quest to put her rapist behind bars, the recovery then non-recovery in 1980s New York, reckless behaviour, drugs, moving to California, a new start at writing, meeting her husband.

Domestic happiness . . . where Sebold washed up in her late 30s like a shipwreck . . . won't be a threat to her production. "I wasn't able to write very well the whole time I was in my darkest mood, " she says now. "I had to get to the place where I could write well . . . I'll try not to get too happy but, you know what, that's not really a threat." She's right.

The Almost Moon grew out of this mood and stability, and is even darker yet than The Lovely Bones: somewhere between Patricia Highsmith and Stephen King. After all, this novel has a much more complicated, ambiguous sense of victimhood, and it begins with one of the most swiftly plotted lines in recent memory.

"When all is said and done, killing my mother came easily, " says Helen Knightly after smothering her 88-year-old mother. Mrs Knightly was suffering from dementia.

"It's a shock that I am suddenly being accused of being bleak, " Sebold says. But there is something far darker about The Almost Moon than The Lovely Bones, which told the story of a raped and murdered 14-year-old girl who looks down from heaven as her death remains unsolved.

Helen's is not a freak crime of malicious intent, nor even a loving attempt to put her mother out of a degrading misery. It is a fantasy of revenge, acted out.

"Once begun, " Helen says, "I did not stop. She struggled, her blueveined hands, with the rings she feared would be stolen if she ever took them off, grabbed at my arms. . . I held the towels for a long time, staring right at her, until I felt the tip of her nose snap and saw the muscles of her body go suddenly slack and knew that she had died."

Helen tries to cover up her crime, calling on her ex-husband, who flies out from California, and then her best friend's son, whom she takes to bed in a fury. Neither can help, especially as chips of memory drift back, and the reader discovers that Helen and her troubled father lived their lives in thrall to her mother and the mental illness that incapacitated her. In Lucky, Sebold discovered "memory could save, that it had power, that it was often the only resource of the powerless, the oppressed, the brutalized" . In The Almost Moon, she has written a character who turns to that recourse for solace and is crushed by it.

It's hard not to point out the similarities between Helen and Sebold. In Lucky, she described her mother as an ex-alcoholic who took to bed some days, so frail that Sebold's first concern after being raped was to protect her from it. But this new novel owes less to her childhood and more to watching her mother care for her own mother. That's as far as she will go. "If you take all [a writer's] family members, and the dynamics they have, and you put them in a blender, there is a lot of the glue of their work, but not the work itself; the same is true for me. There is this desire . . . and how could you avoid it? . . . to find the roots. But I am not Helen; my mother is not Clair."

The Pennsylvania Sebold writes about remains true to life, only shaded a bit darker, as Katherine Anne Porter did with Texas and Louisiana. "I was talking about Philadelphia with a couple of friends who are New Yorkers, " Sebold says, "and they were saying the difference between New York and Philly is there is a replacement when something breaks in New York.

In Philadelphia they paint over it, put a bright blue coat on top . . . there's a freshen-it-up kind of feeling, layers of patina, a sepia which is also, in my mind, creepier, and richer."

I ask if, in some way, Helen is the self she could have been had she never left, as Rabbit Angstrom was the person John Updike could have been had he never left Shillington. She pauses, and says, "I have seen many people who are unable to break that oppressive, destructive, duty-bound bond . . . not just to a parent who is ill, but a mentally ill parent who can be full of personality and very dominating.

They are. . . inherently more interesting . . . either you break free from that or you don't."

For her, this calls to mind Highsmith, whose work she adores. "A detail about her life which not many people know, " Sebold says: "Her mother tried to abort her by her drinking turpentine, and Highsmith wound up taking care of her in her old age.

Here was this woman who was known as being a people-hater, taking on this incredible burden of a woman who tried to erase her." In other words, people are not their books, and vice versa.

It's not something Sebold has said just to journalists and reading groups. Lucky and The Lovely Bones prompted an avalanche of letters, some disturbing, some amusingly disturbing (fan fiction from grandmothers with ideas for how she could have killed off the rapist in her novel), some of it so involved she has had to disengage. "It's only me and my husband, " she says.

So now, a week after her US publication, Sebold has already begun to retreat. She was on the road for three years with The Lovely Bones, and that part of her life is over. "I think you only learn what kind of personality you have by committing to things." So while she feels grateful for her success, she doesn't feel she owes the world herself in response.

"I'd like to go back to poetry again, " Sebold says, for the first time sounding sheepish. "I really, really revere good poetry. It's been my private discipline." The question remains, though, whether Alice Sebold can have privacy any more.