Sales of second-hand books have almost tripled in two years, the National Trust said.
Income has gone from £573,000 in 2017 to more than £1.4 million so far this financial year, with sales expected to hit £1.8 million, as tens of thousands of books are sold every week – some for as little as 50p.
The rise in popularity has sparked a new wave of book shops opening at National Trust properties, which now total 185.
Over the years there have been many special discoveries at trust book shops, including a signed letter from White Christmas star Bing Crosby tucked into a book.
Autographs from the first climbers to reach the top of Mount Everest – including Sir Edmund Hillary – were found in another.
Property fundraising officer Katy Taheri said: “It’s amazing to see the popularity of our second-hand book shops growing so quickly, not only in terms of the quantity of books being given to us, but also the amount we’re selling.
“It seems the nation still loves to curl up with a good book, with many feeling there’s something extra special about a book that has been flicked through and enjoyed by other people.
“The success of our book shops is down to our brilliant volunteers who, at many properties, have brought great creativity in how to sell books and get our visitors to fall in love with them.
“And as the stories being told prove, our shops aren’t just about the books, they are also about the fascinating discoveries hidden away in the pages, from historical records and images to famous autographs and letters.
“They really are a treasure trove of hidden gems.”
More information can be found at www.nationaltrust.org.uk/second-hand-bookshops.