A rare copy of Harry Potter and the Philosopher's Stone is tipped to fetch as much as £60,000 when it goes under the hammer later this month.
Yahoo UK chatted to Hanson's Associate Director of Books and Works on Paper Jim Spencer for the signs that show a Harry Potter book is worth a lot of money.
He told Yahoo: "I get hundreds of emails every day from people who think they've found a first edition Harry Potter and want to know how much it's worth. But a lot of them end up disappointed.
"A genuine first edition of JK Rowling's first book, Harry Potter and the Philosopher's Stone, in good condition is very scarce.
"A lot of people think they've got a first edition, but technically they aren't. Only 500 first edition hardback copies of the first book were published and 300 went to schools. So they ended up getting read and passed around a lot and I've seen some that a practically falling apart.
"A genuine first edition in good edition is very rare and if it was signed by JK Rowling in 1997 at the time of publication it could be worth £100,000."
The rare first edition hardback copy of JK Rowling's first book up for auction was originally bought for just £10 from the bargain bucket of a bookshop in Scotland back in 1997.
The seller even revealed: "Because it had no dust jacket, I got a couple of pounds knocked off the price. Our two children enjoyed the wizard tale as a bedtime story all through that holiday."
The book was then left to gather dust under the stairs for 26 years before it was recently rediscovered and will by offered up for sale by Hansons Auctioneers at their Derbyshire Saleroom on Monday, 11th December as part of their library auction.
Though slightly worn, it is in good condition and has been given an estimate of £40,000-£60,000.
So what makes an old Harry Potter book worth mega galleons?
Here are the signs your Harry Potter book is so valuable it should be kept in a Gringott's safe.
Title page first edition listing
Only 500 copies of Harry Potter and the Philosopher's Stone were originally printed in hardback.
Jim Spencer revealed he is always being contacted by people who think they have found one - but it is not the original first edition.
The way to tell if you have the original first edition hardback is to look inside title page.
If it says first edition you're already out of luck.
A genuine first edition will say first published in 1997 and crucially NO other date.
The number line will read 10 9 8 7 6 5 4 3 2 1
And there will be no mention of Warner Bros, who produced the film series based on the books.
The first edition of The Philosopher's Stone contains a printing error on page 53. In the list of items Harry must take to Hogwarts "One wand" is listed twice.
But don't get excited it that error is included in your copy. Jim Spencer revealed that the typo was corrected and then somehow made its way back into later editions. So it is the publication date of 1997 only, that makes the difference.
Hard back without dust jacket
The latest copy of Harry Potter and The Philosopher's Stone to be auction off was originally discounted at the buyer's request because it had no dust jacket.
But if you have a first edition hardback with no dust jacket don't be disheartened.
Spencer reveals: "Those first 500 copies were printed and sold without a dust jacket. So that copy would never have had one."
JK Rowling's signature
Harry Potter books that have been signed by JK Rowling can be worth thousands.
But Jim Spencer revealed that the author's signature has changed over time. He explained: "Her early signature was a lot more angular, and then later on it became more loopy as you can see it has been done very quickly."
Books with the early signature which were signed at the time of publication are worth more than those that have been signed at a later date.
Other editions that have been signed by JK Rowling could also have some value.
But Spencer warns the market has been flooded with forgeries.
He revealed: "I have even seen signed copies with tickets from the book signings to show authenticity and the tickets have been forged too. They have even been able to fake the hologram she introduced on tickets to later book signings."
He went on: "A signed copy with a dedication in it is much harder to fake. She writes witty comments to the people she is signing the book for. I looked out for signatures with a dedication, a genuine signing ticket and a signed statement from the person who collected the signature."
Spencer revealed book dealers have been known to attend signing events and offer to donate £1,000 to JK Rowling's children's charity Lumos in return for her signing a first edition and they end up being escorted out by security.
He said: "It sounds like a lot of money to donate to charity, but they will be able to sell the book for much more."
Chamber of Secrets and beyond
The Philosopher's Stone is the most valuable of the Harry Potter books as it is the first.
But a hardback first edition of The Chamber of Secrets or The Prisoner of Azkaban in good condition, with the dust jacket could be worth up to £1,000.
Spencer warns: "From the fourth book onwards millions of copies were printed. People get excited when they think they have a first edition, but they are not very rare."
Limited edition collectables
Earlier this year an uncorrected proof copy of Harry Potter and the Philosopher's Stone failed to sell at auction after it did make the reserve price of £15,000.
Spencer said: "It was surprising as that is technically rarer than a first edition.
"But people who love Harry Potter want to have the thing that appeared on the shelves and feel what it must have felt like at the time to hold that very first book in their hand. That is what makes them so desirable."
There are a few limited edition Harry Potter books that Spencer says are worth holding on to, but they are worth hundreds, not thousands.
The deluxe edition Harry Potter books which are bound in cloth of different colours - red for Philosopher's Stone, blue for Chamber of Secrets and green for Prisoner of Azkaban do have some value. They are worth more if the cellophane wrappers have never been opened. A full set might fetch £2,000.
The 2008 limited edition of The Tales of Beedle The Bard is bound in velvet with fake precious stones and was sold in a leather case.
Spencer said: "It is attractive, but not big money."
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