I'm currently reading the novel Prince of Thieves by Chuck Hogan, which inspired the recent movie The Town. So far it's richer and denser than its cinematic version, but there's no doubt that Ben Affleck's screenplay captured the essence of the book.
Then it's on to the original novel Winter's Bone and I previously read Ben Mezrich's infamous opus The Accidental Billionaires, which became The Social Network.
For me, it's fun to read a book that a film is based on because it's interesting to see how the writer overcame (or failed to overcome) the transition from book to screen. For example, Aaron Sorkin had in some respects a real challenge on his hands with Mezrich's book. It's a slight tale which jumps all over the place and has no likeable hero.
However, Sorkin managed to get around this by taking the elements of the book that worked and discarding the ones that didn't. Friends of the real Mark Zuckerberg claim that he is nowhere near as witty or charismatic as the onscreen version (and bear in mind that Sorkin writes him as someone who's quite likely autistic).
But film people are smarter than us, have better one liners and have more dramatic lives - and Sorkin's script manages the feat that Mezrich's book only aims for - making the story of Facebook into a gripping tale of power and betrayal.
Sometimes the novel is better than the film, sometimes a film takes a sow's ear of a book and creates a cinematic silk purse. I think the best cases are where the film compliments the book but creates a stand-alone work of its own.
Also on my mind is the idea of killer premises. You know the way sometimes you hear an idea for a movie and think, "Yes, I'd watch that?" Wrecked, starring Adrien Brody, is just such a film - check out the trailer. I'll be buying a ticket anyway....