Ah, I loved the Artemis Fowl books when I was younger, great suggestion.
I'm a keen fan of J.R.R. Tolkien, and love the adaptations of The Hobbit and the Lord of the Rings trilogy, but I would highly recommend Tolkien's 'The Silmarillion', both as a candidate for a big screen adaptation and if you've not already read it! It's a prequel to all things concerning the Bagginses, Gandalf, Gollum and all the rest. Despite it only being one volume, I'd put it on a par with George R. R. Martin's 'A Song of Ice and Fire' in terms of the scope and scale of its storyline, and not to mention dark enough to rival G. R. R. Martin when it comes to heaping on the tragedy! It's certainly not short on action either, and I think could certainly translate on to the big screen.