People with large book collections are being encouraged to take a look through their shelves for one book that could be worth up to £80,000 - some 100 years after it was released09:13, 11 Sep 2026Households with book collections are being encouraged to take a look through their shelves to see if they are sitting on a fortune. Over the years we can accumulate a lot of books, whether you're a book worm yourself, and can't help but pick up a few whenever you're out, or have recently had a family member's entire collection passed down to you when they have passed on.‌But did you know there are some books that are worth a small fortune, despite them being bought over 100 years ago? This is true for one specific Agatha Christie book, which was bought for 37p upon release, but could now be worth up to £80,000.‌A first edition of her novel, The Secret Adversary, is worth just £5,000 without its original dust jacket, but £80,000 with it, a 16 times difference from one paper cover.‌The figures come from WeBuyBooks' valuation data on the UK's most valuable novels.Mike Lane, CEO and co-founder of WeBuyBooks, said: "We've seen families keep the book but bin the cover without realising it held most of the value."The Secret Adversary is a 1922 mystery and thriller novel by Agatha Christie that introduces her famous sleuthing duo, Tommy Beresford and Tuppence Cowley.‌The two broke young friends, start a business called Young Adventurers Ltd. to find work with the first advert reading ‘willing to do anything, go anywhere’.The book, which was Christie's second, was a commercial success that actually sold better than her debut, The Mysterious Affair at Styles.‌However, this isn't the only Christie book that could be worth a small fortune, with a first edition of The Mysterious Affair at Styles being worth a huge £100,000 today.An expert from WeBuyBooks said: "Over the years, Agatha Christie has been a figurehead in the murder mystery genre, drawing in fans from across the globe and building a franchise that has seen countless TV and film adaptations."In total Agatha Christie has written and published 66 novels, each being met with varying levels of success, so it will come as no surprise that she has made it onto this list with The Mysterious Affair at Styles.Article continues below"If you are lucky enough to find a first edition of The Mysterious Affair at Styles in 'very good' condition with its original dust jacket, it could be worth up to £100,000."Now is your opportunity to finish your cuppa and check out your bookshelves to see if you have any hidden gems tucked away that could make you a fortune."