If you are coming to "Do Androids Dream..." by way of "Blade Runner", the film (loosely) based on the book, be warned: the two are similar only in their most basic plot outlines. As is typical of Dick in his prolific middle period (roughly 1962-1970), there is a lot going on in this novel. The main theme, dehumanization, is amplified by each character and situation, but Dick creates a rich environment that is equally compelling as the way that theme is explored.
In short, Rick Deckard's job is to kill renegade androids, a job he finds taking its toll on him. Sadly, he's not the only one who is feeling dehumanized: witness the existence of the Penfield Mood Organ (one of Dick's most touching inventions), through which one can alter one's state of consciousness by dialing the appropriate setting (such as "the desire to watch television, no matter what's on"); witness the cult around Wilbur Mercer, a vague messianic figure whose (literally) uphill struggle and persecution an individual can share by grasping the handles of a little black "empathy box"; witness Buster Friendly, a television personality bent on exposing Mercerism as a sham; and, lastly, witness the popularity of artificial animals (such as the electric sheep of the title) in a post-apocalyptic world where most real animals are either dead or sterile from radiation.
That Dick manages all of these sharply drawn ideas (and more, as well as a number of interesting characters) while still keeping the plot moving swiftly and ruminating on the nature of humanity is a tribute to his brilliance. "Do Androids Dream..." is not a perfect book -- there are a few loose ends at novel's close -- but it is a rich and rewarding one that retains its impact as the years pass. As a summation of several of Dick's ideas, it may also be the ideal introduction to this author's work.