Encyclopaedia of Potterworld

"I have been enjoying sharing information about Harry’s world on Pottermore for free, and don’t have any firm plans to publish it in book form."

- J. K. Rowling FAQ answer, confirming she no longer has any solid plans for this book

The Encyclopaedia of Potterworld, also called the Scottish Book, is a planned guidebook by J. K. Rowling as the authoritive directory of all the creatures, characters, places, and other elements that comprise the Harry Potter universe, containing mostly un-published notes, letters, drawings, etc. As of May 2012, this project appears to been postponed or cancelled in favour of Pottermore.

Publication
In a (somewhat) recent interview with PotterCast, Rowling revealed she definitely intends to write the encyclopedia, but wished not to rush the process.

In court testimony in April 2008 (regarding grounds of copyright infringement) Rowling stated that she had 'recently' begun working on the project.

On 4 September, 2009, the Leaky Cauldron website reported that Rowling's fellow author, friend, and neighbour, Ian Rankin, mentioned in a BBC interview that Rowling had been "making family trees of all her characters", presumably for the encyclopedia.

On 13 April, 2012, she confirmed that she had started work on the project, and that all royalties made from the project would be donated to charity.

However, in May 2012, Rowling updated her official site to say that she no longer had "firm plans" to publish an encyclopedia in book form, saying that she was currently choosing to share information on Pottermore for free instead.

Contents
If published, subjects covered might include the method of creating a Horcrux, the manner in which Peter Pettigrew gave Lord Voldemort a rudimentary body, and the reasons for Florean Fortescue's murder.

Behind the scenes

 * J. K. Rowling's calling it "The Scottish Book" is a reference to the way the play is called "The Scottish Play," as it is considered bad luck to speak the play's name out loud, particularly before a performance.