One is a 30-year-old London actress whose novel was plucked from the slush pile, another an American school teacher who has been working on his story for more than 10 years, the third a 28-year-old web administrator at the University of East Anglia. Together, they are the debut authors who set this week's London Book Fair on fire, each commanding huge sums from the publishers from around the world who were frantic to acquire their novels, and collectively reminding a book trade which spent this week debating how fast the literary world is changing that, just sometimes, it's still all about the stories.

Matthew Thomas, 38, has decided to quit his job as a high school teacher in New York to focus on writing full time after a US publisher paid more than a million dollars for American rights in his debut We Are Not Ourselves, and a British press spent six figures to land the novel. Described as an "Irish epic" , it follows the story of Eileen, raised in 1940s Queens by an alcoholic mother and a union-employed father, as she grows up, marries, and early-onset Alzheimer's affects her family.

"I've been working on this book in different forms for more years than I like to remember," says Thomas. "I started in the writing seminars at Johns Hopkins in the fall of 2000, but I had been writing my way around this material before that, during my undergraduate years at Chicago, in workshops with the wonderful and recently deceased Richard Stern. I submitted short stories to workshop at Hopkins, and later at Irvine, and worked on We Are Not Ourselves on the side, until I finally submitted a portion of it in my last workshop at Irvine.

"Some of those stories inevitably provided material that I reshaped and worked into the novel, which is fortunate, because they didn't work as stories. I tried telling this book in all sorts of ways, from different points of view and in different voices, until I settled on a working method. It was a long road, and there were far more years when it wasn't working than when it was – when it was shaggy, messy, hopeless – but in the last four years or so things seemed to click and the writing came more easily. The book beat me up until I was sufficiently beaten, and then it sat me down and taught me how to write it."

His agent, Bill Clegg, at WME, says he knew he had something outside the ordinary in his hands as soon as he began reading We Are Not Ourselves. "In the opening pages I knew I would be reading every 700-plus pages of the manuscript. There was an authenticity to the voice and a command of language that was instantly apparent. I stayed up until 3.30 am finishing the novel and was devastated," he says. "As tired as I was I began to read again from the beginning because I was not quite yet ready to let go of this family and the heart-breaking story Matthew tells. Soon after, once I had submitted to editors and publishers in New York and abroad, it was clear that I was not the only one to have had that experience. The book casts a powerful spell."

Thomas is astonished at the attention his debut has received. "[It] exceeds any hopes or expectations I might have had for it," he says. "I wanted to write a book that conveyed ideas I had about the human condition, certainly, but at root what I wanted to do was make readers feel something – something genuine, though, not something unearned. Sentiment without sentimentality was always my goal."

This week's London Book Fair also saw a host of other big-money deals but the debut novelists are the ones to have set international publishing buzzing. "It has been refreshing and inspiring … to see there is genuine appetite for new voices in fiction," says Thomas's UK agent Elizabeth Sheinkman at WME.

In the UK, 28-year-old Emma Healey is still reeling at how fast her world has changed. Her debut, Strange Companions, is currently the centre of a fierce auction in the UK, with nine publishers bidding to acquire it – she comes out of her open plan office at UEA to discuss how it feels. "On Easter Monday I was still writing the book – now three weeks later there's all this interest. I'm just completely stunned," she says. "It's fantastic – when you're writing a novel the thing you most want is to connect with other people, and especially with this, as it's such a personal book, inspired by my grandparents."

Strange Companions is narrated by Maud, in the midst of fast-progressing dementia, who tries to find her best friend Elizabeth, leaving notes around the flat to remind her of her quest while failing to recognise her family and carers as her mind returns her to the 1940s. It is the first thing Healey has written. "I wouldn't say I've even written short stories before. It was just this story which kept nagging at me, and it felt like terrible training material because it's so complicated, I would tie myself up in knots. But I couldn't concentrate on anything else," she says.

Karolina Sutton at Curtis Brown, her agent, met Healey after she did a talk at the UEA creative writing course. "She submitted her novel to me and I read it overnight," said Sutton. "[It's] gripping, moving and at times funny. It illuminates the mystery of memory and identity. For anyone who has ever met a person with dementia, it brings a pang of recognition and for a moment we can experience their point of view, which is very moving."

The offers, says Sutton, are still "flooding in". "With the level we are at right now, you can safely say it will be one of the biggest books of the fair. The response has been really fantastic with publishers truly engaging with the story, presenting their bids in very imaginative ways. One bid arrived by taxi in a 1940s suitcase full of period items which appear in the novel, another was accompanied by handwritten notes from all members of the staff, from the CEO to sales and marketing executives."

An 11-publisher auction for actress and former Oxford student Jessie Burton, meanwhile, led to a six-figure deal in the UK earlier this week, and another in the US, for her debut The Miniaturist, after agent Juliet Mushens at The Agency Group picked the novel off her bulging slush pile.

"I have had 400 submissions that way since December," says Mushens. "I remember loving her cover letter because she referenced the fact that I had recently read a book she based her research on, and she said she 'liked my style' which made me laugh. The first three chapters absolutely got under my skin. When I was halfway through the full manuscript I emailed her to ask if she had signed with anyone else, to which she told me she had four offers from other agents. When I finished it I called her and asked her to meet. We clicked instantly, and had a shared editorial vision for the book which is very important. I can feel a special book somewhere in my stomach. It is hard to put into words – more an instinct than anything scientific. The Miniaturist is about gender, secrets, love, power, sexuality … It is poetic and provocative, and so assured, it is hard to believe it is her first book. I fell in love with it and was almost bereft to finish it."

Set in 17th-century Amsterdam, The Miniaturist tells the story of 18-year-old Nella, who is given a miniature replica of her home by her new husband, and begins to see the dramas of her household mirrored in miniature form. Burton says it was born out of a visit to the Rijksmuseum in Amsterdam.

"There is a dolls' house there that is more than a dolls' house. It is enormous, breath-taking, a symbol of the wealth and power of the Dutch Golden Age. Men, women and children catch sight of it and sigh with wonder. It is an exact replica of the owner's house and cost the same as a full blown townhouse to build and furnish. I asked myself, what kind of society allowed such extravagance, and why? I saw this young woman, Nella, turning up to her new marital home, full of a sense of wonder, unaware that so much adversity in this rich and hypocritical society was waiting round the corner for her. It is a story about how much or little we can control our fate, how slenderly we may know a person, how frugality and luxury, love and hate, the domestic and the public spheres of life are inextricable."

She "wrote and rewrote it" in the second half of 2010 and over the next two years, "in theatre dressing rooms, and secretly in city offices", and says she has "run out of hyperbole" to describe the situation of the last week. "It has been like a sustained carnival with its quieter moments of disbelief and delight. And yes, a little terror. It is so exciting to me to know that the story I have told will be read in languages from Norwegian to Japanese and I feel more than privileged that publishers worldwide have taken the novel to their hearts."

But despite the international book deals pouring in – Canada, Brazil, Germany, Italy, France, Portugal, Serbia and Holland, Turkey and Norway, as well as the US and the UK – Burton isn't planning to quit her job quite yet. "I think balance is so important. When I was temping, the boredom of that set itself up nicely as an opposition to what I really wanted, which was to find an agent and get published. It fuelled the hunger to change the way things were going for me. It was, if you like, a comforting struggle. My mum has already told me to get a job. And I always do what my mum says."