Source (in Spanish): Here is my quick translation:
Carlos Ruiz Zafón, author of The Shadow of the Wind, will publish next April 17, his new novel, with a print run of one million copies, according to an announcement this morning (February 28th) by Editorial Planeta. The publisher considers that this print run will reach a historical landmark in Spain.
The number of copies (printed) surpasses the 525,000 for World Without End by Ken Follet, of which, in its day, the publisher Random House Mondadori explained that it was about "the most number of books ever placed in Spanish bookstores in a single day," and that it found "was more than the number for the Harry Potter series."
Ruiz Zafón's new work, untitled [now known to be El Juego del Ángel], will tell a story of ambient intrigue in the Barcelona of the 1920s and will return to submerging the reader in the Cementery of Lost Books, scene from his previous book.
Ruiz Zafón is considered by his publisher to be the Spanish author most read in the world. The Shadow of the Wind, published in May 2001, has been published in 50 countries and sold more than 10 million copies. This new entry (in the planned tetralogy around the Cementary of Lost Books), which is published 7 years after its predecessor, will form part of a tetralogy. The publisher has chosen this date for its publication to fall on Saint George's Day.
Sadly, it's not yet available for purchase on Amazon, but trust me, as soon as I can, I'm getting a copy of it and I'll review it to give people an idea of the book's quality well in advance of its releases en otros idiomas.
Edit: While it'll likely be a year or longer before the English translation is released, for those of us who can read Spanish, there is an official website for the book now up. Not much yet, but there is a place where you can have information sent to you (in Spanish, of course) regarding updates on the author or any other author on Planeta's roll.