The one faithful film adaptation of a PKD story I'm aware of was the Linklater version of A Scanner Darkly. All the others take a major conceptual element of the story's basic premise, but then seriously alter the narrative in ways that often make them very different thematically. I really liked the Linklater film, too, because I think the "slavish" recreation of the story does a far better job of presenting the ideas that Dick had in their full nuance and depth than any other film version of his work ever has.) Most other adaptations of his work (there are some I haven't seen) tend to fall far short of that, which is really a shame. I mean, Blade Runner (the 1982 version) is a great movie. I like it a lot, but the novel has layers of philosophical depth that the film just doesn't get anywhere near. “Do Androids Dream of Electric Sheep?” is one of Dick's many explorations of what was clearly his favorite philosophical topic, namely "what is the difference between reality and an illusion?" The movie is reasonably accurate in its representation of the basic plot points (a police officer hunts for escaped androids from space colonies, who are illegally living on Earth and posing as humans) but doesn't even attempt to probe the weirder, but more thought-provoking elements of the story--e.g. that the human race is actually going extinct, and that the robots' brains are distinguishable from those of humans by the robots' inability to feel empathy toward living things.
If you're into SF, read on.