I thought of two more, Blade Runner and Total Recall are both (very loosely) based on Philip K Dick stories... and I just remembered Minority Report is too. However both Total Recall and Minority Report are based on short stories which would be impossible to turn into movies... as for Blade Runner, the book (which was called "Do Androids Dream of Electric Sheep") was completely wacko. If you've never read it I would recommend it, honestly that guy must have been doing some serious drugs when he wrote that book. Actually all the stuff I have read by him is pretty out there, another great one is "Ubik". Great story, but some very strange characters...