Nelson Mandela’s memoir, a sequel to his 1995 autobiography Long Walk to Freedom, will be published in 2016.
The book will be based on a hand-written draft and completed by Nelson Mandela’s former advisers.
Nelson Mandela’s widow, Graca Machel, said he began work on the manuscript in 1998, towards the end of his five-year presidential term.
Publishers Pan Macmillan said the book would be “candid and clear-eyed about the difficulties he faced in office”.
Graca Machel said Nelson Mandela saw it as “a natural progression” from Long Walk to Freedom which covered his early years, his political struggle against South Africa’s apartheid regime, and the 27 years he spent in prison.
The book went on to become one of the best-selling political memoirs of all time.
Editorial director Georgina Morley said the new book, based on material from the Nelson Mandela Foundation’s archives, would “remind readers everywhere what he stood for”.
An exact publication date was not announced.
Nelson Mandela was released from prison in 1990 and went on to win the presidency in South Africa’s first all-race election in 1994.
He won the Nobel Peace Prize, along with former South African President F.W. de Klerk, in 1993 for negotiating the end of white-minority rule.
Nelson Mandela stepped down in 1999 to concentrate on charity work.
Literary agent Jonny Geller said the book would be an important historical document.
“A lot of it is a political memoir about being president, his relationships with the army, with the unions and with the tribes. What’s really interesting is that he can’t help but talk about leadership and talk about the most important thing which is the transition from freedom to power.
“This will be a very inspiring book because it’s actually about what you do when you actually have power.”
Mandela: Long Walk to Freedom, a Nelson Mandela biopic presented at Toronto Film Festival, does not shy away from the less flattering aspects of his character, according to British star Idris Elba.
“It was important we had both sides, the good and the bad,” said Idris Elba.
Early scenes in Justin Chadwick’s film show Nelson Mandela as a womanizer who was violent to his first wife Evelyn.
“I didn’t want to deface Mr. Mandela in any way,” Idris Elba continued.
“But I didn’t want to portray him in a way that wasn’t honest.”
Idris Elba was speaking at the Toronto Film Festival, where Mandela: Long Walk to Freedom had its world premiere this weekend.
Based on the former South African president’s autobiography, the film charts his early life as a lawyer, his political activism and the 27 years of imprisonment that preceded his democratic election in 1994.
Naomie Harris plays Nelson Mandela’s second wife Winnie in Justin Chadwick’s two-and-a-half hour drama.
Nelson Mandela new biopic does not shy away from the less flattering aspects of the character
The film has had a mixed reception from critics, with one calling it “more dutifully reverential than revelatory or exciting”.
“We’ve seen the saintly Mandela we all know and love,” continued Idris Elba, who did not meet “Madiba” before embarking on the project.
“It was important for us to take the audience on a journey prior to that and understand who he was.”
Nelson Mandela, now 95, was released from hospital last week after three months of treatment for a recurring lung infection.
“Like everybody I’ve been very concerned for his health but I’ve been keeping optimistic,” Idris Elba told reporters on Sunday.
According to Justin Chadwick, Idris Elba was the right person for the biopic despite being from England and bearing little physical resemblance to its subject.
“There were other obvious choices, but Idris was the brave choice,” he said.
“He doesn’t look like Madiba, but we weren’t going for a lookalike, soundalike version.”
“Idris managed to capture the Mandela magic,” agreed Terry Pheto, the South African actress who plays Evelyn in the film.
Morgan Freeman, Danny Glover, David Harewood and Sidney Poitier are among the others to have portrayed Nelson Mandela on film and television.
Idris Elba, whose other films include summer blockbusters Thor and Pacific Rim, has been singled out for praise by critics who have seen the film in Toronto.
Mandela: Long Walk to Freedom is one of several Toronto titles this year to draw their inspiration from real-life figures.
Julian Assange, Jimi Hendrix and Britain’s Got Talent winner Paul Potts also feature in films in this year’s line-up.
The launch of Justin Chadwick’s film coincides with the UK release of Diana, a biographical drama about Princess Diana, that drew a withering response from the British media.