Your Harry Potter books could be even more magical than you thought.
It might not occur to 90s kids that their well-worn copies of JK Rowling's novels could be worth any money – but they could actually be very valuable indeed.
Abe Books, who sold a first edition of Harry Potter and the Philosopher's Stone for £26,700, have created a useful guide to rare and collectible JK Rowling novels.
Firstly, anything signed by the author is clearly valuable – a book signed by one of the illustrators less so.
While different editions might be worth a good deal of money, the real treasure is a 1997 first edition of Harry Potter and the Philosopher's Stone
"Hardcover first edition first printings of this 1997 book have become the 'Holy Grail' for Potter collectors," the guide explains. "If you find one in the attic, then you've hit the jackpot. Only 500 were published and 300 went to libraries.
"The main characteristics of a 1997 first edition first printing are a print line that reads "10 9 8 7 6 5 4 3 2 1" and the crediting of "Joanne Rowling" not J.K. Prices on AbeBooks vary from £28,850 to £39,700."
This video goes through the different editions of Harry Potter books. Find out whether a trip to Gringotts is in order today...