Hilary Mantel has won the £50,000 Man Booker Prize for her novel Bring up the Bodies, the sequel to Wolf Hall, which won the prize in 2009.
Mantel is the first woman and the first living British author to win the prestigious literary prize twice.
"This double accolade is uniquely deserved," said Sir Peter Stothard, chairman of the judges.
The book is about Thomas Cromwell, an adviser to King Henry VIII, and charts the bloody downfall of Anne Boleyn.
It is the second book in a trilogy.
A third instalment, to be called The Mirror and the Light, will continue Cromwell's story until his execution in 1540.
Mantel was announced as the winner at London's Guildhall on Tuesday night.
Mantel's win also makes her the first person in Man Booker history to win the prize for a direct sequel. She is only the third double winner of the award, after JM Coetzee and Peter Carey.
Receiving her award, she joked: "You wait 20 years for a Booker Prize and two come along at once."
She added: "I know how privileged and lucky I am to be standing here tonight. I regard this as an act of faith and a vote of confidence."
As well as the £50,000 cheque she also receives £2,500 for being shortlisted, along with the other five novelists in the race.
Sir Peter said that the judges had made their final decision on Tuesday after a "lengthy and forensic examination".
He said: "This is a very remarkable piece of English prose that transcends the work already written by a great English prose writer.
"This is a bloody story about the death of Anne Boleyn, but Hilary Mantel is a writer who thinks through the blood. She uses her power of prose to create moral ambiguity and the real uncertainty of political life."
He added: "She has recast the most essential period of our modern English history; we have the greatest modern English prose writer reviving possibly one of the best known pieces of English history.
"It is well-trodden territory with an inevitable outcome, and yet she is able to bring it to life as though for the first time."
Asked whether the book qualified as a thriller, Sir Peter referenced The Godfather: "You can see as much Don Corleone in this book as DH Lawrence."
Jonathan Ruppin, web editor at Foyles bookshops, said: "Bring Up the Bodies has remained a strong seller since it was published in May, but this rare double Man Booker win confirms her output as essential reading.
"Mantel has been writing superb fiction for much longer than she has been winning major awards, so many readers will soon discover that she is their new favourite author. There's every possibility she might pull off a unique treble when she completes the trilogy."
The impact on sales for a Man Booker winner is considerable - every winning book since 1996 has grossed more than £1m.
Yan Martel's Life of Pi, which won in 2002, made just under £10m.
Last year's winner, Julian Barnes's The Sense of an Ending, has sold 300,000 copies so far.
According to the latest figures, Mantel's Bring up the Bodies has sold 108,342 copies, which is more than the other 11 Man Booker longlisted novels combined.
Mantel was previously longlisted in 2005 for Beyond Black. She was a judge for the prize in 1990 when AS Byatt won with Possession.