One specific observation has to do with Deliverance. The four men seem a lot stupider in the book, or perhaps I should say that page by page, one has time to notice it. The movie races along, as a movie will, and the manly survivalism of the Burt Reynolds character is convincing (and well-performed) enough that you may not stop to think, what kind of survivalism is this, that heads into unknown terrain without doing a lick of research? That character on the page seems like a madman from the get-go, and the others complete fools for going along with his concept.

So probably the movie has the advantage over the novel in encouraging us to accept that these are successful businessmen in over their heads, and not simply four dimwits.