If any city conjures up a mental image of quintessential Englishness, it is Bath. Dickensian street lighting and Georgian terraces, notices on street corners announcing winter concerts and couples warming themselves by the roaring fires of old-fashioned inns. It is in such a place that I meet one of the best new authors of this year, Samantha Harvey. The location is important. Many new novelists would prefer to talk in a swanky London restaurant near their publishers, but it's rather apt that Harvey suggests the city where she lives. Her debut, The Wilderness, is a work of outsider fiction a long way from life in the capital: at its heart is not some cooly-detached metropolitan type plucked from Harvey's own life experiences, but a 60-year-old man called Jake, suffering from Alzheimer's disease and living in windswept Lincolnshire. As Harvey will later admit, building a narrative out of mental collapse is quite a challenge for a 34-year-old first-time novelist. It's quite a proposition for the reader, too.
But the way Jake tries - and often fails - to piece the shards of his life together over the course of the novel is gut-wrenching, heartbreaking and, crucially, compulsively readable. In a way, it becomes a detective story as Jake reveals fragments of his life both real and imagined as a husband, father and architect. Harvey tantalisingly leaves mysterious clues about relationships and long-lost children hanging in the air.
Such subject matter means The Wilderness, though rewarding, is occasionally demanding, so to find Harvey refreshingly easy going when we meet is a surprise. Although, perhaps it shouldn't be. Harvey's life has changed a lot over the last year: she has been shortlisted for the Orange Prize, longlisted for the Mann Booker and won the Betty Trask Prize. As we speak, she is basking in the glow of being shortlisted for the Guardian First Book Award.
"I really can't believe what's happened to me," she says. "You really do have your moments where you wake up and realise the magnitude of what you've achieved. It's honestly changed the way I see myself: I feel like a proper, valid writer who can make a career out of this. It's been..." Harvey grapples for the word. "Magnificent." The reason Harvey feels so good is not just because of the recognition. It is because The Wilderness is a great achievement: writing a book is something Harvey has always wanted to do, but the specifics of this particular novel were a huge challenge, taking over three years. Often chapters were torn up and thrown away. In fact, Harvey rolls her eyes as she remembers a time when the main idea behind the book - Jake's memories becoming increasingly elusive and unreliable - wasn't fully formed.
"It was a horrible, chaotic, terrible, neurotic process involving hundreds of thousands of lost words," she grimaces. But like a fine sculptor gradually chiselling away at rough stone, she found the story in the end. "I knew that I wanted to write about somebody getting dementia and convey what that might be like," she recalls. "But it took a long time to work out how that would work in a novel, how I could merge stories, Jake's history and the present day."
But work it out she did. Harvey manages to create the effect of Jake's confusion - and fantasies - without ever confusing the reader. The Wilderness soon becomes more than a book about what might have happened, what did happen and what Jake has imagined. As he slips away in his present, he tries to hold on to an increasingly misty version of his past. It is a novel in which the very nature of memory and mortality is explored.
"Way back, I was inspired by Iris Murdoch having Alzheimer's. When she was alive, it intrigued me to think of this brilliant woman and what she had become. People often ask me if I have experienced dementia in my family, and in a purely artistic way that's a great compliment because, no, I haven't at all. I didn't know anything about Alzheimer's beforehand, which, rightly, made me paranoid about getting it right. There's nothing worse than a book which uses some sort of device like this to tell its story and then gets the medical elements all wrong, so I had to do a lot of research. But I liked that in a way: it was completely new territory for me."
Harvey is not aware of any other novels on dementia written from the sufferer's point of view. That might be why The Wilderness is on so many awards lists this year. But this isn't a "worthy" book. It has won so much praise because it could easily have been an experimental, non-linear piece. A set of disconnected stories in which Jake merely flails around in a world he can no longer place. Instead, Harvey has woven a coherent - and sad - narrative of humour and humanity.
"There were two responsibilities in my view, one to the subject matter and one to the story," she says. "I was continually asking myself how much I could leave unresolved as far as the narrative was concerned, because that obviously fitted very well with how Jake was feeling. Now, having read some of the reviews, having looked at the book again, I'm not positive I got it exactly right." Harvey is refreshingly honest and unaffected throughout our time together, but I am surprised that, unprompted, she is prepared to pick over The Wilderness's few failings in such detail.
"Is it too confusing? Did I fulfil the story I set out to write at the start? I thought about these things when I was writing," she says. However, these are not significant problems. In fact, one of The Wilderness's great strengths is that it keeps the reader guessing until the very end, repeating stories but changing crucial facts as Jake's mind plays tricks on him. To prove her point, Harvey then asks me how I think one of the main characters dies: from Jake's stories there are a number of outcomes.
So as not to spoil the novel for those yet to read it, all I can say is that I get it spectacularly wrong. "You see!" she laughs. "I had a lot of fun piecing the narrative together and leaving clues that could be solved. But some are buried very, very deep. Perhaps too deep, on reflection. Only one person I've spoken to has got that death right. If I'm justifying it, I'd say that the mechanics of the death aren't that important; it is how it affected Jake.
"It was a gamble to take on a story written in this way, both for me and a publisher," she adds. "I didn't really think it would get published. Even my agent was worried." But the gamble pays off because Jake is such a believable character, despite the reader's increasing difficulty in the veracity of what he is saying. A post-war architect consumed by the possibilities of concrete, his whole life's project was to take his family from London to Lincolnshire and build a house for them all to live in. Ironically, as we learn from the very first chapter, one of his buildings ends up being the prison his son is later incarcerated in. His profession, like most things in The Wilderness, is laden with meaning: Jake has spent his whole life building things and yet the very structure of his own life is collapsing around him.
"The architect thing was maybe a bit heavy-handed," Harvey worries again. "But I liked the resonances, especially that he worked with concrete and that by the time he retired, many of the structures had already been knocked down because they were seen as unsightly. I don't know why I didn't make him a happier character - his life had gone wrong well before he has Alzheimer's. But I think that's the novelist's natural instinct: to be interested in where lives have gone wrong rather than right.
"He's struggling with his sense of self, looking at his life and feeling generally dissatisfied. In my thinking he over-eggs the unsuccessful side of himself. If you think it's strange that I can create this character and then chide him for not being more positive, then it was deliberate. I was trying to get to the heart of why memory is so selective - how you pick the bits you want and make a version of yourself out of that. They're not always the whole truth, are they? What we see of Jake is what he decides is the truth about himself, which is sad, really."
Searching for the truth in the story is why The Wilderness is a work of literature rather than a plea to understand Alzheimer's disease. However, the by-product of such a beautiful book is that it achieves this too. I ask Harvey whether, despite the numerous narrative dead-ends and a completely unreliable narrator, you can, if you look hard enough, find a story in this novel that actually happens, that is the "truth".
"I don't know if I agree with you that Jake is completely unreliable," she says. "If I'm reading a book where the narrator is so unbelievable I end up getting bored and uninterested:what's the point, essentially? So, I didn't want everything to be up for grabs: there is a truth to The Wilderness, it's a mystery with a certain number of things you can resolve. For this book to work, I certainly needed to know what happened and what didn't - and I do. I don't expect other people to work it all out, but what's important to understand, I think, is that Jake is never trying to trick anyone. He's always trying to find the truth.
"So I don't know what kind of book that makes it. A thriller without any thrills, maybe!" And with that, Harvey laughs one last time, wraps herself up against the damp Bath day, and strides out into the chilly streets festooned with twinkling lights. She must, she says, hurry back to work on a follow-up. "A straightforward, linear novel," she jokes, with some relief. For her sake, I hope she's serious.
The Wilderness (Jonathan Cape) is out now.