JK Rowling's fifth Harry Potter book, Harry Potter and the Order of the Phoenix, is set to hit shops worldwide on 21 June.
The manuscript has been delivered to publishers Bloomsbury & Scholastic and will go on sale simultaneously around the world.
Nigel Newton, chief executive of Bloomsbury Publishing, has described the book as "brilliant and utterly compelling".
The publishers have revealed that boy wizard Harry will be told a secret which will change his world forever.
An extract from the book reads: "Dumbledore lowered his hands and surveyed Harry through his half-moon glasses. It is time,' he said, 'for me to tell you what I should have told you five years ago, Harry. Please sit down. I am going to tell you everything'."
