A series of moving letters which the best-selling crime writer collected over the years have been released for the first time to mark what would have been her 125th birthday.
Christie, who died in 1976, hoarded hundreds of messages from her readers, including a note from a woman telling how the novels helped her survive a labour camp in Germany, and another who shared the stories from memory with inmates while she spent 12 years a Romanian prison with no access to books.
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The newly-released letters include one from author PG Wodehouse and another from a Polish woman who exchanged a piece of candle for a Polish translation of Christie's The Man in the Brown Suit, in a war-time labour camp in Germany.
"I read and re-read (it) so often that I almost knew it by heart," she wrote.
"The first few pages were missing so I didn't know the title or the author but for seven months it was my only link with a normal world.
"I know your writings have given pleasure and amusement to millions of people all over the world but never can one of your books have meant more to anyone than that tattered Polish translation did to me."
Christie, who penned 66 detective novels and 14 short-story collections, also kept letter written in 1963 by a woman who spent over a decade in a Romanian prison with no access to books.
The woman wrote: "During the 12 years I spent in prison I never saw a written page.
"My memory, however, could not be sealed up and thanks to it and to you my fellow-sufferers came to know and to love the works of Agatha Christie."
Christie also saved a note from PG Wodehouse, the English writer best known for the Jeeves and Blandings Castle novels and short stories.
His 1969 letter from New York stated that he was "pleased and proud" after discovering she had dedicated Halloween Party to him and added "a new Agatha Christie is always an event".
Praising her choice of title Wodehouse also revealed that he found "getting a satisfactory title is the most difficult problem".
Christie also treasured a 1958 letter from a 14-year-old boy in Bristol who started a book club at his school so he could raise funds to buy her work.
"I have bought 28 books by you and this is how I have managed it," he wrote.
"I charge the boys 3d per book to read at school, and 6d if they wished to take them home.
"With the money I obtained . . . I bought more 'AC' books . . . Now my scheme is bringing in so much money, I can afford to buy one of your books a week."
In her typed response, which Christie also kept a copy of, she replied: "I was very interested in your letter. You seem to have had a very good idea and I congratulate you."
Christie's grandson Mathew Prichard published a number of the letters and replies to mark her 125th anniversary and encouraged today's fans to share their experience of her writing.
"Knowing what receiving these letters meant to my grandmother, I'm sure she would be moved to see these personal stories shared publicly for the first time," Mr Prichard added.
"As we call to her fans across the globe to share their stories and experiences of Christie, I look forward to discovering how her work continues to inspire today."