I had intended to do a fair amount of fiction writing. Didn't get around to any of it. But I did respond to everyone who asked for an inner-animal guess in my previous thread, which is a good feeling; and I read through the novel The Prestige, on which last year's movie was based.
It was a good reminder of why movies will never be able to fully replace books.
Prestige: The Movie and Prestige: The Book diverge fairly radically from each other. I didn't understand why until I was more than halfway through. Because Prestige: The Book is in itself two separate stories. The actions of the two magicians are told twice, and exactly twice -- once from the point of view of each rival.
It's a book that you cannot read in a linear fashion. Once you reach the second half, you have to read it in parallel -- constantly flipping back and forth to contrast the two retellings of the same scene. You begin to notice that even the dialogue differs when the two characters interacted directly; and it's strongly hinted that, through editing or omission, not one but both of the characters are unreliable narrators, twisting the truth to paint themselves in a better light.
There is no objective or omniscient view of the characters' conflict. You only have their words against each other; and it's that tension that gives the book its impact.
I don't think you can do that in a movie.
There's something about a visual image that forces a certain omniscience. The camera is itself a character in the scene; it observes impartially, it records accurately. To do otherwise -- to have what's on screen be an inaccurate representation of the film's events -- would break cinematic expectation so badly that no major studio would touch such a film with an eleven-foot pole.
The counterexamples are probably few enough to be listed by name; and the only one that comes immediately to mind is Hero, in which certain scenes are later revealed in a plot-important way to be complete fabrications of their narrator. But to have a clearly demarcated wavy-lined flashback be overturned is one thing; to have the central events of the film later called into question is a recipe for audience confusion.*
(Edited to add: "Rashomon" and "The Usual Suspects" have also been cited in multiple comments. It's interesting to note that, so far, every one of these movies is about character(s) telling a story. That extra layer of abstraction is necessary to hew away the instinctive rules of cinema.)
The implicit rules are different in a novel. There is no camera to provide a single, omniscient vision of the plot; there is only a narrator (omniscient or internal) retelling it. There is more freedom to play meta-games.
There's an extra investment to taking stories from the written word, but there's also a richer payoff.
* This isn't to say the dramatic reveal can't be done well; cf. The Sixth Sense. But that's not seen events being redefined; that's context being added to chilling effect.