The deluxe edition of
Harry Potter and the Half-Blood Prince will feature unique drawings by American artist Mary GrandPré, who has illustrated all previous U.S. editions of the novels.
The book will have a slipcase and will include a 32-page insert with "black-and-white art from the book blown up to full-page size," according to updated listing information.
The "unique" art will presumably not feature in the regular editions of the book.
This US special edition is 704 pages long, because of the extra drawings.
The UK will also have a special edition of
Half-Blood Prince which will only be avaliable from
October of this year.
UPDATE:
The Leaky Cauldron is now reporting that Amazon.co.uk have the UK special edition down for release on October the 3rd of this year.
Source:
HPANA 
UPDATED: 'Deluxe' Half-Blood Prince (US & UK) 
