This novel is set in a post-apocalyptic future in which the earth is almost uninhabitable because of a recent nuclear war. A lot of animals are extinct or nearly extinct, and a lot of humans have emigrated to Mars to ensure that the human race would not die of radiation. And, as an incentive for people to emigrate to Mars, the governments promised to give them free androids that would be their servants on Mars.
However, some androids have killed their masters and have secretly travelled back to earth, where they disguise themselves as regular humans. They are physically undistinguishable from real humans, and the only ways to tell them apart from real humans are to give them empathy-tests (robots are not empathetic) or to run tests using their bone marrows. Thus, it becomes very difficult for the police to hunt down these escaped robots.
The novel focuses on Rick Deckard, a bounty hunter whose job is to hunt the androids and "retire" (i.e., kill) them. He has to track these robots down, give them the empathy test (to make sure that they're robots), and then kill them using his laser gun. At the end,
he succeeds in his mission in retiring all the escaped androids.
Overall, this novel wasn't bad, but there were a lot of holes and illogical parts in it. For example, if the androids were really that smart and dangerous, why wouldn't they have gotten guns for their self-protection? And, there were simply too many things that went unexplained, such as the "mood dialling" that was at the beginning of the novel.
Also, I found the electric animals and the concept of Mercerism to be a lot more fascinating than the actions in the novel. These parts gave me a lot to think about, and I wish the author had expanded more on them.
So in short, I think the author could have made this novel more coherent, and instead of focusing on all the actions, he could have focused more on the more philosophical parts.