The much-anticipated follow-up to Harper Lee's classic novel To Kill A Mockingbird has gone on sale, with bookshops around the country staying open all night to cope with demand.
The tome, Go Set A Watchman, is guaranteed to be a summertime best seller, 55 years after Lee's book about a rape trial in the racially-divided deep south of the US first hit bookshelves.
The original story and its central characters - Scout, her brother Jem and their lawyer father Atticus - are known and loved by millions of readers around the world.
But many have been left "baffled and distressed" at the revelation the new book paints Atticus as a racist "bigot" who went to a Ku Klux Klan meeting.
Fans around the country spent the night camped outside stores as strict rules prevented copies of the novel going on sale any earlier than midnight.
Sandy Phillips, a project manager, compared reading the first chapter to "finding out that Father Christmas beats his reindeer".
Ms Phillips added: "I do not think it will have the same resonance but that's not to say that I won't enjoy reading it."
Ashleigh O'Connell was first in line to get a copy at Waterstones' Piccadilly store, having arrived at 6pm to get her spot.
Ms O'Connell was "sceptical" when she first heard about the follow-up.
She said: "To Kill A Mockingbird is so perfect I know it is not going to be the same so I am trying to see it as separate."
Go Set A Watchman revolves around the now-adult Scout's return to her native Alabama from New York to visit her father.
A New York Times review revealed the plot twist, telling readers: "We remember Atticus Finch in Harper Lee's 1960 classic, To Kill A Mockingbird, as that novel's moral conscience: kind, wise, honourable, an avatar of integrity who used his gifts as a lawyer to defend a black man falsely accused of raping a white woman in a small Alabama town filled with prejudice and hatred in the 1930s."
It adds: "Shockingly, in Ms Lee's long-awaited novel, Go Set A Watchman, Atticus is a racist who once attended a Klan meeting, who says things like, 'The Negroes down here are still in their childhood as a people'. Or asks his daughter: 'Do you want Negroes by the carload in our schools and churches and theatres? Do you want them in our world?'."
News of the new book's publication stunned the literary world earlier this year and concerns were raised about the extent of Lee's involvement in the project.
Her agent was forced to respond to reports suggesting the 88-year-old was being taken advantage of over the publication of the book.
Authorities in her native Alabama closed their investigation into the issue saying the reclusive writer had ''made it quite clear'' she wanted the book published.
Fan Valerie Walcott, 52, who was counting down the hours until midnight, said she understood Lee's decision to portray Atticus as imperfect, adding: "There's absolutely no way that he cannot be a product of his environment."
Author Joanna Trollope, who took part in a panel discussion at the Piccadilly launch, urged readers to be "grown up" in their understanding of the new novel.
She said: "I think we have all got to be a bit grown up about this.
"The thing about mockingbird is we all think we own it and she wrote it for us and we read it privately. So we have got to let go of that."
She added: "Maybe we won't be able to possess it quite as much as before."
Also at the launch was was Shami Chakrabarti, director of human rights organisation Liberty, who said To Kill A Mockingbird had inspired her to become a lawyer. She said the novel showed "what law can do for real people and our communities".
She added: "For me it was a wonderful, wonderful 20th-century morality tale. It was one of the most important things I have ever read."
Labour MP Diane Abbott, who is hoping to become the next London mayor, said Lee's first novel had made a "lasting impact" on her.
Referring to Michael Gove's controversial move to push American literature off the school syllabus, Ms Abbott said: "I do not think everything Michael Gove says is wrong but it was very, very foolish to try and ban books."