The Testaments, Margaret Atwood’s much-anticipated sequel to her feminist dystopia The Handmaid’s Tale, has landed her a place on the Booker prize shortlist – despite the fact that barely anyone has read it yet.

With little publicly known beyond that it is set more than 15 years after Atwood’s hero Offred attempted to escape a theocratic future US, the plot of The Testaments remains under lock and key for most readers until its global release date on 10 September, with midnight launches and bookshop parties planned around the world.

Chair of judges and Hay festival director Peter Florence said it was an “extraordinarily complicated process” to get copies of the manuscript, which is protected by a “ferocious” non-disclosure agreement. He could not say more than that it is a “savage and beautiful novel, and it speaks to us today, all around the world, with particular conviction and power”.

“The bar is set particularly high for Atwood and she soars over it,” he said. “I can’t wait for everyone to read it.”

This is the sixth Booker nomination for the Canadian author, who won the ’ prize in 2000 for The Blind Assassin. She is set to face off against another former winner, Salman Rushdie, who is nominated for Quichotte, a retelling of Cervantes’ Don Quixote set in today’s US. Rushdie’s 14th novel has not gone down well with critics; the Observer felt it was “rarely as funny as Rushdie thinks it is”, while the New York Times said his books were “increasingly wobbly, bloated and mannered”.

Judge and editor Liz Calder, who published Rushdie’s 1981 Booker winner, Midnight’s Children, denied there had been any bias at play and said they had not worked together for decades. “It is barely even a friendship,” she said. “It was once.”

Florence said: “If you are going to make a tilt at one of the greatest works of literature, you better hope you can play at Cervantes’ level,” adding that Rushdie’s novel is “a hell of a ride”.

The giant underdog of the shortlist is Lucy Ellmann’s Ducks, Newburyport, published by tiny, Norwich independent Galley Beggar Press. A 1,000-page monologue of an angst-ridden homemaker in Ohio, the British-American author’s book unfolds in a single sentence and spans love, climate change, gun violence and the condition of the US. Judge and composer Joanna MacGregor called the book an example of “radical literary form and voice” and, despite its hefty size, praised it for flowing “with dazzling light and speed”.

British novelist Bernardine Evaristo is nominated for Girl, Woman, Other. Following 12 characters, most of them black British women, the novel sees some stories overlapping to make connections between disparate humans. Judge and author Xiaolu Guo called it “impressive and fierce … there is never a single moment of dullness”.

Nigerian novelist Chigozie Obioma makes the shortlist for An Orchestra of Minorities. Narrated by a chi, a guardian spirit in Igbo myth, the novel follows Nonso, an ambitious Nigerian graduate who becomes trapped in Cyprus after falling for an education scam. Judge and journalist Afua Hirsch called it “a crucial journey into a heartache that is both mythical and real”.

Turkish novelist Elif Shafak is nominated for 10 Minutes 38 Seconds in This Strange World, described by Calder as “audacious and dazzlingly original”. Set in Istanbul, the novel portrays in the final moments of a murdered sex worker’s life as her brain slowly shuts down.

Florence said he had previously felt that Booker judges had said “deeply daft things about the need for cracking stories and relatable characters and stylistic adventure” in fiction.

“Now find I agree with absolutely everything they’ve said,” he said. “Is it too much to want a book to be adventurous, to be formally inventive, to have an emotional and intellectual core that grips you and sends you to new places, and deep into yourself, to understand how the world might be? I don’t think it is.”

Four of the six shortlisted books are published by imprints of the giant conglomerate Penguin Random House. Prize rules stipulate that imprints that have never been longlisted can only submit one book a year, while previously nominated publishers can submit up to five. Florence denied that PRH’s dominance suggested the rules needed reworking: “Given their bidding power, and the range, scale and quality of their editorial talent, maybe this is a great year for PRH but two or three books should be their minimum target grade.

“I would be more than happy to announce any of these six as the winner and feel we had got something spectacular and wonderful that would convince someone who read one book a year as well as [literary critic] Gillian Beer,” he said.

The winner, who takes home £50,000, will be announced on 14 October at a ceremony in London.

The 2019 Booker prize shortlist

The Testaments by Margaret Atwood (Vintage, Chatto & Windus)

Ducks, Newburyport by Lucy Ellmann (Galley Beggar Press)

Girl, Woman, Other by Bernardine Evaristo (Hamish Hamilton)

An Orchestra of Minorities by Chigozie Obioma (Little, Brown)

Quichotte by Salman Rushdie (Jonathan Cape)

10 Minutes 38 Seconds in This Strange World by Elif Shafak (Viking)