The main character, Sebastian Dangerfield, is both "one of the most famous characters in Irish fiction" and an utter bastard; needless to say, the right actor is required to render him tolerable on screen, let alone likable. For that reason alone, it's easy to understand why Donleavy has traditionally refused to allow the book to be made into a movie, despite repeated attempts. Now, though, after an encouraging meeting with Depp, the author has reportedly changed his mind: "Mr Depp is something else. He is very bright, extremely intelligent, and very knowledgeable."
No other information is available about the film, and it will doubtless be a while before it can get started since Pirates of the Caribbean 3 is not expected to really get going until this summer.