Personally I think it is all about focus. Movies are great because they are done and over in two hours (more or less) and you feel satisfied (hopefully) in the end, ready to move on. Reading books take a bit more of a commitment - depending on how life goes for you, you can usually get one done at least within a week or less and again - satisfied.
In all honesty I don't really have anything to equate it too for him. Nothing that will really show him what it feels like. It is my dream to get a book published and yet I feel like I'm falling further and further behind on accomplishing that goal. I need to push myself ad whole lot harder and strengthen my resolve to stay focused. If I don't drift off to watch tv or scan the internet then the progress will hopefully prompt some of the enthusiasm that I've been missing so desperately.