An entire generation has well-thumbed Harry Potter books lurking in cardboard boxes at their parents’ houses, and some of them could be goldmines.

Online book marketplace AbeBooks, which specialises in rare books, has detailed exactly which editions are worth a good deal more than their cost price – ranging from £200 to over $50,000.

Here’s what to look out for:

Harry Potter and the Philosopher’s Stone

‘Hardcover first edition first printings of this 1997 book have become the ‘Holy Grail’ for Potter collectors…Only 500 were published and 300 went to libraries. The main characteristics of a 1997 first edition first issue are a print line that reads 10 9 8 7 6 5 4 3 2 1 and the crediting of “Joanne Rowling” not JK. Prices on AbeBooks vary from $40,000 to $55,000. A handful of advance proof copies are available from $7,500 to $13,500.’

The first editions of the deluxe edition from 1999 are also desirable with prices from $450 to $2,500. Paperback first editions of the Philosopher’s Stone are also quite scare and attract four-figure price-tags – sometimes five figures if in excellent condition.’

Harry Potter and the Sorcerer’s Stone (US title)

‘Prices for first edition first printings go up to around $6,500 with a fair selection between $4,000 and $5,000 – many signed by the author – although cheaper copies can be found.’

US first editions will have the number line of 1 3 5 7 9 10 8 6 4 2 8 9/9 0/0 01 02,” on the copyright page along with “Printed in the U.S.A.23″ and “First American edition, October 1998”. Prices for later editions in good condition are in three figures.’

Harry Potter and the Chamber of Secrets

‘Prices for hardcover first edition first printings go up to $9,000. In 1998, JK Rowling was still a jobbing author rather than a worldwide superstar richer than the Queen, so there are a reasonable number of signed first editions available from her book tour signings. Deluxe editions can be priced in four figures if signed.’

Harry Potter and the Prisoner of Azkaban

‘The initial hardcover print run was stopped mid-printing after it was discovered that ‘Joanne Rowling’ rather than ‘JK Rowling’ had been printed on the copyright page. Joanne versions are available for prices starting at around £1,500 and go up to $12,000 for signed pristine copies.

First edition first printings will have the number line 10 9 8 7 6 5 4 3 2 1 and a block of misaligned text on page seven. Opinions about the number of copies printed before the errors were spotted vary greatly – however, it seems that only a small number came off the press which greatly enhances its value.

The deluxe editions, with green cloth, of 1999 are also collectible if they are a first edition (prices go up to $5,000). However second printings can be picked up for three figures.’

Harry Potter and the Goblet of Fire

‘JK’s signature (by book 4, she was signing fewer copies) turns any first edition of Goblet of Fire into a book with a four-figure price-tag but there are a handful of copies over $10,000. Look out for the limited editions with original watercolour illustrations by Giles Greenfield (Bloomsbury’s UK edition) and Mary GrandPre (Scholastic’s super rare US edition of only 25 copies). If either illustrator has signed a copy, then prices are again in four-figures. Many buyers are also looking for books accompanied by items such as entrance wristbands or golden tickets from events where JK Rowling has conducted a signing.’

Harry Potter and the Order of the Phoenix

‘Look out for first edition copies signed by JK Rowling at the midnight launch event in Edinburgh on 2003 that are going to be priced in four figures. Jason Cockroft illustrated the UK edition while Mary GrandPre illustrated the US version – their signatures enhance a book’s value but such copies can be found for as little as $200.’

Harry Potter and the Half Blood Prince

‘Published in July 2005 to widespread Pottermania, JK’s days of book tours were long gone so very few signed copies are on the market. A handful are available for prices up to $5,000.’