Engines of Creation: K. Eric Drexler. Anchor Books/Doubleday, originally published in 1986.
If you are going to read one non-technical book on nanotechnology, this is the one. Drexler describes how a manufacturing technology could develop in which the basic parts are individual atoms precisely placed according to design, rather than handled in "unruly herds". He explains how we can think about technologies that have not yet been developed, and explores both the opportunities and the perils that these technologis will present, and discusses how we can prepare for their coming. Explore Engines on the web, but to have your own copy of the book, order here.