This is a semi-animated film by the guy who did Scanner Darkly (based on PKD's novel).
It follows a dream-life state of one guy -- the protagonist -- in a really trippy, lucid manner. It's very philosophical and there are conversations about reality, free will, the relationship of the subject with others, and the meaning of life. Along the way the film touches on other topics including existentialism, situationist politics, posthumanity... (thank you wikipedia)
Oh, and it mentions Philip K Dick's Flow My Tears, The Policeman Said. It has a conversation about it. PKD would of loved to have seen this film if he were alive... Really does him justice there. The book sounds like it was written from a different dimension or something.
It's impossible to say too little and difficult to say a substantial amount about this film. I definitely recommend it. It's got multiple watches in it due to the subjects it covers. Perhaps some of these will help you get a feel for it...:
"They say that dreams are only real as long as they last. Couldn't you say the same thing about life?" -- That may as well be a PKD quote.
(Film is based on Santayana's Maxim) - "Sanity is a madness put to good uses; waking life is a dream controlled." - George Santayana