I found the movie and the book so different in pacing and tone that they are hardly comparable. The book really has the ethical and sociological questions as the meat, and uses the plot simply as a backbone. The movie does the exact opposite, with the plot the driving force and the questions as food for further thought. You can still enjoy the movie without thinking too hard, if you wish, but the book will fall flat without giving it a lot of thought. As an example, the movie completely drops Mercerism, likely because it would be slow and clunky to try and explain it in an action movie. But it is an essential part of the book, without which PKD's explorations of the pain of the conflict between individualism and collectivism would be entirely missed. Similarly with the artificial animals, which are shown only in passing in the movie, but are a central tool in the book to illustrate hypocrisy and jealousy in people trying to grasp at what is "real". The titles of the two works encapsulate this difference of direction perfectly.