Also, if you're going to read only one book about linguistics, I'm not sure if The Language Instict is a good choice. It's very fun and informative, but Pinker does a very bad job of clarifying which claims are a matter of consensus, and which ones his own, at least somewhat controversial opinions. Also, linguistics is a wider field than you might conclude from the book, with lots of fascinating insight about all kinds of things that Pinker doesn't talk about.

For a good introduction to linguistics, I recommend R.L. Trask's Language: the Basics instead. It's much shorter, but definitely better as a primer.