Overview book about economic theories
Snowdon and Vane "Modern Macroeconomics: Its Origins, Development And Current State" is probably the best book I have read which gives a clear exposition of all the major macroeoconomic schools from the classicals to the New Keynesians. It highlights what the different schools have contributed to modern macroeoconomics and compares them to the other schools. They even include interviews with economists such as Robert Lucas Jr. and Milton Friedman to mention a few. I guess this is exactly the book you are looking for and to be honest I think every single person studying economics should read this book. It is not an introductionary economics book but I think most people should be able to read and understand it.