Cryptography: An Introduction (2011) [pdf]
If you just want to get somebody interested in cyptography, I HIGHLY recommend: The Code Book (http://amzn.com/0385495323). It's a great read for anybody who's done a little bit of history by walking you through the role of cryptography and hiding messages throughout history.Covers most everything in the context of war history as far back and shaving a person's head, writing a message on it and then letting the hair grow back to hide it. Great read that will lay the groundwork of interest for a lot of people.