NEW YORK : The boy wizard Harry Potter is growing from strength to strength. Online distributor Amazon.com has said that the latest instalment in the Harry Potter book series has already become its fastest-selling new product ever, with more than 500,000 copies ordered in advance of the book's publication on 21 June.

Harry Potter and the Order of the Phoenix has already surpassed Harry Potter and the Goblet of Fire as Amazon.com's largest new product release ever. In total the online retailer said that it has received more than 875,000 orders for the book on all of its Web sites worldwide, including the 500,000 ordered on www.amazon.com.

On the flips side a Reuters report indicates that fears that the book could potentially leak onto the Internet or even street corners before its official release, has printers, retailers, freight firms and the publisher maintaining a veil of secrecy on anything surrounding its pending shipment into thousands of stores and homes.

The book's launch is expected to mark the largest single online distribution event of any one item, with hundreds of thousands of copies already pre-ordered over the Internet. Amazon.com has an added pressure: It promised those who pre-ordered by a certain date that they would receive the book on the very day it's launched -- which happens to be a Saturday the report states.

J.K. Rowling's fifth book in her Harry Potter series has a massive initial print-run, of which 8.5 million copies have been earmarked for the US alone. Films have already been made on Rowling's first two books. The third film is scheduled for a release next year.