Two previous Booker Prize winners have been shortlisted for the literary award this year.
Sir Salman Rushdie and Margaret Atwood are in the running to win the prize for a second time after making the final six.
Judging of Atwood’s work was shrouded in secrecy.
The shortlist for the coveted annual honour was announced at the British Library in London on Tuesday.
Sir Salman has made the list for his referential work Quichotte, and Atwood for her sequel to The Handmaid’s Tale, The Testaments.
Atwood’s work has yet to be published, which resulted in an “extraordinarily complex” process of non-disclosure agreements in order for the judging panel to be able to read it, according to Booker chairman Peter Florence.
He said: “The fact there is a book that generates this extraordinary amount of care in the reading world is something to be treasured.”
The novel was offered up through watermarked copies which the judges each held in a safe place to avoid any spoilers from the highly-anticipated work leaking out.
Atwood previously won the prize for The Blind Assassin in 2000, and Sir Salman claimed the award for Midnight’s Children in 1981.
Hay Festival founder Mr Florence said of Rushdie’s ambition for Quichotte: “You better push the boundaries of fiction. You better have something to say about the contemporary world.
“Rushdie is tilting at Cervantes.”
Other shortlisted authors for the 2019 Booker are Lucy Ellmann for Ducks, Newburyport; Bernardine Evaristo for Girl, Woman, Other; Chigozie Obioma for An Orchestra Of Minorities; and Elif Shafak for 10 Minutes 38 Seconds In This Strange World.
Mr Florence said: “There are strong cases to be made for all of these books. I would be happy to announce any of these the winner.
“They all have novelty, they are genuinely novel.”
Last year, the first Northern Irish winner, Anna Burns, claimed the prize for her work on societal coercion of women, Milkman.
The panel which will decide the ultimate winner of the literary award includes publisher and editor Liz Calder, novelist and film-maker Xiaolu Guo, writer and former barrister Afua Hirsch, and composer Joanna MacGregor.