Many of you may remember the movie version of this book starring Harrison Ford: "Bladerunner." The movie became a cult favorite and yet still didn't cover all of the concepts of the book.
The book takes place in a post-apocalytpic world in which due to the radioactive fallout, Earth's citizens are asked to emigrate, one incentive is that each emigrating family will receive a custom-built android servant (colloquially referred to as an "andy"). Here's where the trouble begins. Many androids escape the Earth colonies to return to Earth and avoid slavery. On Earth those that have chosen to stay behind risk the chance of radiation causing permanent damage and in order to combat the gloom have mood organs which the citizens can simply dial up whatever mood they want for the day. Also a new religion, Mercerism has taken hold and the citizens worship through a device called an empathy box. In this they witness the fable of Wilbur Mercer who had the power to bring animals back from the dead. The government destroyed that power by using radiation on the part of his brain that allowed him that power. This forced Mercer into the "tomb world." He strives to reverse the decay of the tomb world and ascend back to Earth by climbing an enormous hill. His adversaries throw rocks at him along the way (inflicting actual physical injuries on the adherents "fused" with Mercer), until he reaches the top, when the cycle starts again.
The runaway androids must be destroyed and this story centers around a bounty hunter whose job it is to destroy the "andys." Rick Deckard, an active bounty hunter for the San Francisco Police Department, prepares for a typical work day. He feeds his electric sheep as per usual to prevent his neighbor from suspecting its true nature. Meanwhile, his wife spends her days at home under the influence of the empathy box and mood organ.
At the police station Deckard learns that the active senior hunter Dave Holden has been incapacitated by a Nexus-6, the most advanced and humanistic type of android created to date. Deckard is chosen to find the six remaining Nexus-6 models in the San Francisco area. This also is where the main theme of the book is carried. The androids are incapable of empathy, so through a series of tests to determine empathy, an android is discovered. However, Deckard starts to wonder whether he is an android because he can kill or "retire" the androids with no empathy. When he does realize he has empathy toward the androids he then decieds he cannot do his job. The battle within himself and the empathy discovered in Mercerism allows us all to realize what it takes to be human.
Great Sci-Fi, and a rather fun book to read.