Do Androids Dream of Electric Sheep? by Philip K. Dick (1968)
Here we have the famous inspiration for the movie Bladerunner, which isn't necessarily all that much like the novel. As I recall, Bladerunner features a crowded Los Angeles...
Rick Deckard, android bounty hunter, is having a pretty rotten time of it, but he gets his chance when a notice of six rogue androids comes in. If he can take them out, the bounties will really help his finances, and let him buy a real animal again. In this future depopulated earth, many animals are extinct and people are required to own and care for one. (It's a status symbol to have a big animal, and Deckard's real sheep died a while back, so he replaced it with an electric one.) The trouble is, androids are always being made better, and these are the new model Nexus-6; smarter and tougher than plain old humans, the only way to detect them is to administer an empathy test. As Decker hunts for androids across the near-empty San Francisco Bay Area, he experiences mental and emotional turmoil around the question of what androids really are.
Like most PKD novels, this one is fairly bizarre, involves a future Bay Area, and kind of goes all over the place. There is a lot about humanity's new religion, Mercerism, and electric vs. real animals. The planet is covered in radioactive dust, so nearly everyone has left for colonies on other planets; if they go, they get an android servant to do all their work. Androids may not come to Earth, but sometimes they escape and try to hide, which is where Decker's job comes in. Anyone who lives on Earth long enough eventually suffers genetic damage from the radiation, and at that point they may not leave.
It's a pretty good read, strange and questioning. A classic of SF, of course. I'm going to try to read Ubik, too, and I don't know what that one is about.