A Northampton volunteer sorting through a bag of books at a charity warehouse uncovered a handwritten note and autographed book by children's author Enid Blyton.
Bob Twiselton, 70, from Northampton, discovered the signed fourth edition copy of "The Twins at St Clare's", published in 1943, buried in a haul of books donated to the Cynthia Spencer Hospice collection point in Moulton Park.
Inside the front cover is a handwritten note by the Famous Five author herself, addressed to a fan named Barbara, that has been hidden between the pages for decades.
It was Bob's first day on the job when he uncovered the find on August 18.
He said: "I never expected it. I was sorting through the books and saw her name on the spine, and I thought, 'this might be worth something'. But then I opened it and saw it was signed by her too."
The note appears to be a reply from Enid to a fan named Barbara who wrote to the author asking for a copy of her book.
The note from Enid to her fan reads: "You sent me such a nice little letter that for once in a way I will do what I usually cannot do - send you a book of mine.
"Yours with love, Enid Blyton."
The Cynthia Spencer warehouse specialises in posting donations on eBay, but the charity says they think the book could go to auction.
Charity administrator Debbie Roe said: "We're quite amazed at it. We don't know what we want to do with it yet.
"It could have got thrown away buy thankfully Bob is so meticulous. It makes you think how many of our books have come through without us realising their real value."
With no sending address, there are no clues who Barbara could be or who donated it to the charity.