"Knowledge and the Wealth of Nations" by David Warsh (2007). It's really two books: It shows how the academic field of Economics works today, and covers much of the field's history; and it also examines Paul Romer's theory of economic growth, which (succinctly) states that technological advancement is the key factor. Talk to any economist about growth these days, and they'll talk about Romer.<p>It's a very readable book, and I highly recommend it to a wide audience.