How strange that two of the most unnerving thriller debuts of the year tackle the same subject: memory loss. Yet aside from this, Before I Go to Sleep (Doubleday £12.99), by British author SJ Watson, and Turn of Mind (Harvill Secker £12.99), by US writer Alice LaPlante, couldn't be more different. In Watson's novel, the story is told by Christine, married to Ben and suffering from a type of amnesia that means her memories are wiped away every time she goes to sleep. She wakes in bed, a middle-aged man beside her, flees from what she thinks is a one-night stand only to be told this man is her husband, that she is not in her 20s but is in fact 47. "In my life there is a then, a before, though before what I cannot say, and there is a now, and there is nothing between the two but a long, silent emptiness that has led me here, to me and him, in this house." Ben leaves for work. Christine discovers a journal she has been keeping: "Don't trust Ben" is emblazoned on the first page. Already optioned for film by Ridley Scott, Before I Go to Sleep is a nerve-jangling journey down the rabbit hole of Christine's mind, towards the deadly secrets waiting at the bottom.

In Turn of Mind, the story is told by Jennifer, 64, a once brilliant hand surgeon who is trekking wearily out into the wastes of Alzheimer's. In contrast to Christine, LaPlante's narrator is not a victim but a suspect: her best friend, Amanda, has been killed and the fingers of her right hand surgically removed. Using, like Watson, the device of a journal to trace the thoughts of her confused narrator, LaPlante has written a harrowing, moving exploration of a mind falling slowly away from the world.

Another chilling debut comes from the Economist's former Moscow correspondent AD Miller. The Booker-shortlisted Snowdrops (Atlantic £7.99) is the confession of English lawyer Nick, his detailing of the time he spent in Moscow and how his obsession with the mysterious Masha leads him to a dark and dangerous place. It's as eloquent on life in Moscow, a city where even in the summer "you could feel the cold germinating in the warmth", as it is on Nick's descent into corruption. In Russia, writes Miller, "there are no business stories. And there are no politics stories. There are no love stories. There are only crime stories." This holds its own with the best of them.

Guilt suffuses the pages of Mississippi author Tom Franklin's Crooked Letter, Crooked Letter (Pan £7.99) as well. It is, at heart, the story of the unlikely childhood friendship between Larry Ott, a lonely white boy, and Silas Jones, the poor black son of a single mother. Now adults, they haven't spoken for years. Silas is the small Mississippi town policeman; Larry has been ostracised ever since a teenage girl vanished after a date with him years ago. Although nothing was proved, when 19-year-old Tina Rutherford disappears, all eyes are on Larry. Franklin's prose is startlingly beautiful, the novel worth reading purely for his evocation of Mississippi, "its odour of rain and worms, dripping trees, the air charged as if lightning had just struck". But what sticks at the end is Franklin's shattering, heart-breaking depiction of loneliness. A deserving winner of the Crime Writers' Association's Gold Dagger for best crime novel of the year.

Altogether less moving, and none the worse for it, is Don Winslow's prequel to Trevanian's classic satire on the spy thriller genre, Shibumi. Winslow's Satori (Headline £6.99) fills in the early life of super-assassin Nicholai Hel, after he is freed from solitary confinement to kill the evil Soviet commissioner to China. Hel is the only man who might be able to do so, thanks to his unprecedented skills in the secret martial art of hoda korosu  the ability to kill using everyday objects. Exhilarating, faintly ridiculous  and as hard to put down as its predecessor.

Memory is to modern sensation novelists what madness was to their Victorian forebears  an anxiety of the age, ripe for exploitation. Perhaps recognition of the internet's infinite capacity is forcing us to consider the limits of our own. Or perhaps the domination of a key strain of popular culture by Philip K Dick has created an ideas vortex from which no one can be bothered to climb free. Whatever your view, the war against cliché desperately needs more troops on the front scattered with blurbs along the lines of "HIS MEMORY IS ALL HE HAS  AND NOW HE WANTS IT BACK".

Sebastian Fitzek's Splinter (translated by John Brownjohn, Corvus, £12.99) was a huge hit in Germany a few years ago. It is, broadly, Eternal Sunshine of the Spotless Mind meets Inception, minus any sense of intellectual curiosity. When Marc Lucas loses his wife and unborn child in a car crash  he was driving  he answers an advert for a clinic specialising in the removal of traumatic memories. He visits the place once, but although he decides not to proceed beyond a few initial tests, it soon becomes obvious that there was more to those tests than the doctors were letting on.

For when he emerges the world has forgotten him. His credit cards stop working. The key to his flat no longer fits. He knocks at the door and it is opened by the wife he believed to be dead  only she doesn't recognise him.

As a genre exercise Splinter is perfectly adequate. Its twists are twisty and its setting in and around the Neukölln area of Berlin is grimly atmospheric. But Fitzek's prose is monomaniacal in its desperation to get you from A to B without any sort of emotional distraction. Marc's reaction to his wife's reappearance  "'I thought you were dead,' he blurted out"  is up there with Lisbeth Salander's to being raped  "'Shit', she thought when he ripped off her T-shirt"  in the pantheon of Eurothriller banality.

Before I Go to Sleep drinks purer water from a deeper well. A first novel by an NHS audiologist who wrote it in between shifts at London's St Thomas's Hospital, it's exceptionally accomplished  like David Nicholls's One Day, a brilliant example of how an unpromisingly high-concept idea can be transformed by skilful execution. In some ways it's an inversion of Borges's story "Funes, the Memorious", about a Uruguayan man who, after an accident, is unable either to forget anything or classify his memories in a way that might stop them overwhelming him.

After surviving what she believes was a car crash, Chrissie developed a form of amnesia which has left her able to store memories for only 24 hours. Every morning when she wakes she has forgotten the circumstances of her life and must relearn them from scratch: who her husband Ben is, where they live, whether or not they have children.

The novel takes the form of a journal she is encouraged to keep by a Dr Nash, who has, without Ben's knowledge, taken an interest in her case. It becomes a lifeline to her past; though of course she has to be reminded every day that she is writing it, or she would never know it existed.

The journal helps Chrissie discover things she has forgotten  for example that she once published a novel. Ben has concealed this and other key facts from her. Why? Is he a saintly carer, feeding her a sanitised version of her life that will not upset her? Or is he manipulating her perception of a world which, without memory to help her decode it, seems to hide innumerable vast conspiracies?

The structure is so dazzling it almost distracts you from the quality of the writing. No question, this is a very literary thriller. It reifies books as memory boxes, dispatches from the dead. It also has  and expects its readers to share  a delicate appreciation of the links between fabulation (that is, the writing of stories that violate readerly expectations) and confabulation (the creation of false memories and experiences by a damaged brain).

The most unnerving aspect of Before I Go to Sleep is the way it is rooted in the domestic, the suburban, the trivial. Forget whizz-bang futurism: it proceeds from ordinary life in tiny, terrifying steps, and is all the better for it. The Escher staircase has an oatmeal carpet.

John O'Connell's novel The Baskerville Legacy will be published by Short Books in September.