Do Androids Dream of Electric Sheep by Philip K. Dick

The book that inspired Bladerunner is well-worth your time regardless of if you have seen the film or not. There is more depth, context and interesting events (like 'dialing desired cognitive states). 
I enjoy explorations of robots and the future interactions between humans and machines.
The title now has multiple meanings because in the book live animals are prized and expensive possessions. Those who can't afford the real thing sometimes buy robotic versions, like sheep. So, humans dream of aquiring real animals, machines might desire something analogous (and, of course, there is the link to counting sheep while trying to sleep).
Great book.