Do you have these Harry Potter books lying around your house? They could be worth up to £40k

TODAY marks 20 years since Harry Potter And The Philosopher’s Stone was first published.

Over the past two decades, the magic surrounding JK Rowling’s popular series certainly hasn’t died down - as collectors still snap up rare books for thousands of pounds.

So do you have any of the novels lying around at home?

With the help of online book marketplace , here’s how to spot if your old Harry Potter editions could make you any money.

From uncommon serial numbers to printing errors, here are the key signs to look out for…

Harry Potter And The Philosopher’s Stone

You may have really hit the jackpot if you have an early edition of JK Rowling’s first fantasy novel.

Sadly, finding one is a tricky task as only 500 of them were printed.

To spot a first edition of the 1997 book, look for a print line that reads: “10 9 8 7 6 5 4 3 2 1”.

You can find these numbers by turning over the front cover of the book and looking at the copyright page.

This typically falls on the second or third page in.

Another tell-tale sign is that the issue will be credited to Joanne Rowling, the name the world-renowned author used before opting to use initials instead.

On Abebooks, these volumes have fetched up to £39,700.

Harry Potter And The Chamber Of Secrets

A first edition of the second book in JK Rowling’s series probably won’t garner as much as The Philosopher’s Stone.

These can typically sell for up to £6,500.

All you need to do is look for the line number “10 9 8 7 6 5 4 3 2 1”.

This price will significantly increase if your copy has been signed by the author.

Harry Potter And The Prisoner Of Azkaban

When the third Harry Potter novel was manufactured, there were a number of errors in the hardcover edition.

Production was halted half-way through after printers noticed that the name “Joanne Rowling” was emblazoned on the front cover instead of “JK Rowling”.

If you have a pristine copy of this edition, you could make up to £8,650.

Harry Potter And The Goblet Of Fire

Due to the surge in Harry Potter mania, JK Rowling was too preoccupied to handwrite her name in as many copies of The Goblet Of Fire.

You could rake in a fortune if you have a signed first edition, which can fetch more than £7,000.

Just look for the print line that reads: “10 9 8 7 6 5 4 3 2 1” on the copyright page.

You’d be lucky to find a copy of the book that has been illustrated by Giles Greenfield.

The beautiful watercolour work on these volumes may also increase the value of your novel.

Harry Potter And The Order Of The Phoenix

In 2003, JK Rowling conducted a Edinburgh book signing to mark the release of her fifth novel.

There are a number of these novels on the AbeBooks website that are listed at prices between £1,010 and £2,300.

Jason Cockrotft and Mary GrandPré were the illustrators behind this edition, but they don’t add a staggering amount of value to the copies.

Despite this, the embellished volumes are typically sold for more than £145.

Harry Potter And The Half-Blood Prince

As Pottermania became an epidemic, JK Rowling had less time to arrange signings and book tours.

Only a handful of author-marked copies are available, and they can garner around £3,600.

If you have a volume signed by illustrator Mary GrandPré, you could make up to £180.

Harry Potter And The Deathly Hallows

As millions upon millions of copies of the final Harry Potter novel were released in bulk, it is difficult to find a novel that’s of considerable value.

In 2007, the author held a book launch at London’s Natural History Museum, where she signed around 1,700 copies.

These rare items have sold from around £720-£4,000.

Last November, a rare jewel-encrusted Harry Potter book was put up for £500,000 at auction.

Although stumbling across such an unusual find is definitely not an everyday occurrence, there are plenty of popular books that can be high in value.

And recently, book expert Pom Harrington told The Sun his top tips on spotting valuable books.