Re: Bladerunner
C. Craig, I like the novel Do Androids Dream of Electric Sheep? There are certainly differences between the book and the movie (such as the absence of Mercer in the move, the absence of Deckard's wife, and Isidore's reduced role), but I see the two as advancing essentially the same themes.
The movie and the book both stress the importance of empathy. Supposedly, the androids lack it, which is what distinguishes them from humans, but the book and the film undermine the distinction. In the book and in the film, we learn that androids / replicants can empathize and love one another. And in the book, as in the film, we see Deckard go from initial detachment to greater empathy. In both book and film, the line between android and human blurs. And in both, the audience's sympathies are engaged--our ability to empathize is expanded--as we feel for the androids. (In the movie, wondering whether Deckard is an replicant is part and parcel of that blurring and perfectly appropriate to that theme.)
Along with an exploration of empathy, the movie and the book both develop a companion theme that other posters have mentioned: the (lack of) difference between the real and the unreal. The book develops this theme more fully than the movie, examining not just "real" humans and "real" animals but "real" moods and "real" philosophies, blurring the line between the two.
And in both the film and the book, Deckard consorts with androids, questions his job, questions himself, and engages in a flurry of active killing.
One of the things I like very much about the book is the way that PK Dick plays with personification to reinforce his themes. In the very first paragraph, "A merry little surge of electricity" contasts with the "unmerry eyes" of Deckard's wife. The electricity has more liveliness--more life--than the humans, who are disengaged from one another and from their own feelings, needing to dial up their moods.
By the end of both film and movie, Deckard is calmer, more at peace with himself, and appreciates that "The electric things have their lives, too" (214).