Don’t get me wrong! Blade Runner is a fine movie. And the book on which it is based, Do Androids Dream of Electric Sheep? by Philip K. Dick, is a very fine book. But these two things don’t really have very much to do with each other. Blade Runner is often touted as a “loose” adaptation, which is why it feels like Ridley Scott and the screenwriters started reading the book, got a few chapters in, thought, “Cool idea. Let’s make a movie,” and then just never finished reading it.
As a result, both are about a bounty hunter named Rick Deckard going after escaped androids, but that’s pretty much where the similarities end. The movie uses terms like “blade runner” and “replicant” (neither of which appear in the book) and takes place in LA rather than post-apocalyptic San Francisco. But the biggest difference between the book and the movie has to do with their overarching themes. The movie stipulates that androids are not all that different from humans; the novel concludes that humans and androids are fundamentally different because humans can feel empathy while androids can’t. This does not, however, necessarily mean that all humans are good.