Another Goodreads review of this book mentions the effects of the books you read before and after a particular book and their influence on your perception of that particular book. My reading of Do Androids Dream of Electric Sheep? was most influenced by 
 Debt: The First 5,000 Years 
 by David Graeber and 
 The Weirwoods 
 by Thomas Burnett Swann. As such, it seemed to me a meditation on the role of slavery in society and the systems that allow the owner class not to feel guilt toward the slave class. 
 (view spoiler)[The androids in this book are not robots. It took me longer than it should have to absorb that information. Dick may not be to blame; perhaps I had just absorbed the idea that droids are robots (likely via George Lucas) prior to even picking up the book. Then again, the androids are clearly regarded by the book's human characters as equivalent to false animals, the inner workings of which are clearly described as mechanical (while the inner workings of androids aren't made as clear). 
 Dick's Andys (he's clever enough to make his diminutive from the significant part of the word, but, I have to admit, it's not as catchy as Lucas's) are more like clones, particularly clones as people who don't understand what cloning is tend to think of them. Unlike ordinary clones, Andys come into being fully grown. The Andys can be differentiated from true humans by measuring their lack of empathy, an ability they may simply not have time to fully develop as they only live for about four years. They are never children, but they are never able to grow up. 
 When I was thinking of the Andys as robots, I could not comprehend any purpose for their existence. They seemed designed solely to pass as human. And that seems to be it. There are so few humans left, particularly healthy ones who might carry on the species, that the colonists on Mars must be spread quite thinly across the planet. They have to have Andys around to stay sane. But the true humans can't become to attached to particular Andys, as they have to form relationships with other true humans in order to procreate. So the religion of Mercerism is established, to ensure that the true humans view the Andys as something other than themselves, as things that can't join in. 
 The Andys' belief that they can defeat Mercerism by debunking it, by bringing to light the facts regarding its origins, simply emphasizes their lack of empathy. Mercer, like the Andys themselves, was created by humans to fill a particular role. Doesn't that make him a counterfeit God in the same way that the Andys are counterfeit people? But both real and counterfeit money are pure fabrications. Value is conferred on one rather than the other only through mutual agreement. (hide spoiler)]