The pressure might have been too much for some writers but not Kate Atkinson: just two years after winning the Costa novel award for Life After Life, a major bestseller hailed as “astonishing” by judges at the time, the novelist has landed the prize again for her follow-up, A God in Ruins.

Described as a “utterly magnificent and in a class of its own. A genius book” by the judges, A God in Ruins tells the story of the second world war bomber pilot Teddy Todd, brother of Ursula, the many versions of whose life and death were recounted by Atkinson in Life After Life.

Taking its title from the Ralph Waldo Emerson quote, “a man is a god in ruins”, the novel, Atkinson’s ninth, beat Man Booker prize winner Anne Enright’s contender The Green Road, Patrick Gale’s A Place Called Winter and Melissa Harrison’s At Hawthorn Time to the best novel prize. The win makes Atkinson the first author ever to land three Costa category awards, after taking the best novel prize for Life After Life in 2013, and the best first novel prize for her debut, Behind the Scenes at the Museum, in 1995.

A God In Ruins by Kate Atkinson Photograph: PR

“A God in Ruins is possibly the best novel I’ve written so it is absolutely wonderful to have it validated in this way,” said Atkinson today. “I’m delighted that it has been chosen as Costa novel of the year, after Life After Life was similarly recognised.”

“I think it’s just astonishing, a stunning, stunning book,” said judge and author Cathy Rentzenbrink, of A God in Ruins. “I don’t think there’s anybody whose life would not be enriched by reading it. It fits with her work, while also being a crowning triumph.”

Rentzenbrink, who judged the best novel prize with the novelist Louise Doughty and the bookseller David Headley, added that A God in Ruins’ author’s note, in which Atkinson writes of how she believes that “all novels are not only fiction but they are about fiction too”, “deserves to win a prize for itself”.

“That’s what this book is doing,” said Rentzenbrink. “You read the whole thing loving it, engrossed in the characters, and then she washes the ground completely from beneath your feet and you realise it was something different all along – it’s so clever.”

Atkinson describes A God in Ruins as “a ‘companion’ piece rather than a sequel” to Life After Life. “When I first decided that I wanted to write a novel set during the second world war I rather grandiosely believed that I could somehow cover the whole conflict in less than half the length of War and Peace. When I realised this was too daunting a challenge – for both reader and writer – I chose the two aspects of the war that interested me most and which I thought provided the richest material – the London blitz and the strategic bombing campaign against Germany,” she writes in her author’s note to the novel.

Life After Life tackles Ursula’s experiences during the blitz, while A God in Ruins follows Teddy’s life as a Halifax pilot in RAF Bomber Command. “Ursula lived many versions of her life in the previous novel, which gave me a certain freedom when it came to Teddy’s own life, many of the details of which are different in this book,” writes Atkinson. “I like to think of A God in Ruins as one of Ursula’s lives, an unwritten one. This sounds like novelist trickery, as indeed it perhaps is, but there’s nothing wrong with a bit of trickery.”

“You don’t at all have to have read Life After Life before you read this one,” said Rentzenbrink. “But if you hadn’t, you would then want to.”

Over 630 books were submitted for this year’s Costa awards, which go to the “most enjoyable” books written by authors resident in the UK and Ireland. Along with Atkinson, four other writers were named as winners in different categories, each of whom will receive £5,000.

Former teacher and librarian Andrew Michael Hurley’s gothic chiller The Loney took the first novel prize, called “as close to the perfect first novel as you can get” by the judges. The Costa biography award went to Andrea Wulf’s The Invention of Nature, a biography of Alexander von Humboldt, the scientist who inspired Charles Darwin but who is almost forgotten today. Judges called it a “thrillingly readable story of a visionary 18th-century scientist and adventurer”.

The Scottish poet Don Paterson won the poetry prize for his new collection 40 Sonnets, praised as “a tour de force by a poet at the height of his powers”, while Frances Hardinge took the children’s award for her “dark, sprawling, fiercely clever” Victorian murder mystery, The Lie Tree.

All five winners will now go forward to compete for the overall Costa book of the year prize, which Atkinson won in 1995 for Behind the Scenes at the Museum. The novelist has already been installed as the favourite to take the top award: bookmaker William Hill gave her odds of 6/4, with Wulf’s biography in second place at 3/1, Hardinge’s children’s novel at 4/1, Paterson at 5/1 and Hurley at 6/1.

If Atkinson wins again this year, she will be the first novelist to do so – although poets Ted Hughes and Seamus Heaney both won the book of the year twice, a novelist never has to date. Worth £30,000, the Costa book of the year prize has been won 11 times by a novel, five times by a first novel, six times by a biography, seven times by a poetry collection and just once by a children’s book. Judges chaired by James Heneage and including Katy Brand, Janet Ellis, Matt Haig and Jane Asher will announce their winner on 26 January.