I havent seen the movie the Ruins yet, but I read the book. While the movie seems to be lambasted for the improbable plot the novel is getting glowing reviews. So the question needs to be asked, is our suspension of disbelief higher for novel than movie or was it just handled better in book form?
I don't think books require you to suspend your beliefs, but to exercise your imagination. Your mind is more actively processing those words into pictures, rather than remaining relatively idle while the pictures are drawn out for you...as in movies.
So, to recap -
Books: words = pictures = emotion
Movies: pictures = emotion
When you leave out a part of the equation, something will always feel like it's missing. That's why subtitled movies rock. *lol*