Pri Oono from Publisher's Weekly has some more info on Charlie's upcoming novel. YAY:

... Kaufman's debut book, it seems, will be more than meta enough for fans long accustomed to his unique movies: it is a novelization of the script for his 2002 film, Adaptation, which itself was based on Susan Orlean's book, The Orchid Thief. Clocking in at a whopping 2456 pages, the book details a midlist novelist's attempt to write the film tie-in for an Oscar-nominated movie.

"He's one of those writers who get paid to turn film scripts into novels," says Charlie, "but the film's release date is approaching, and he hasn't written a word of it because the script is kind of strange and unadaptable -- the script doesn't lend itself to a readable novel. So he kind of gets fed up and writes about his own struggle to write the novel, and in doing so, the novel becomes a huge, sprawling epic only tangentially linked to the actual film."

[...] why write a novel based on a film that was already based on a book? And why now? "I don't know," says Kaufman.

Two editions of Kaufman's novel will be available: the standard novel, and a fully illustrated, limited, deluxe pop-up version which will stand approximately three feet tall. Try putting that on your coffee table.

Grand Central Publishing estimates a release date during the first quarter of 2013. (Source)