I would highly recommend reading Cryptography Engineering [0] cover to cover. It's amazingly readable, covers the basics, the theory necessary to understand how things works and includes ample practical advice and observations on the industry.

The first thing I did after the Snowden leaks was read through the entire thing and after doing so I really wished I had done this years earlier. There's very few books that I think should be required reading across the board for software engineers, but this is one that I do think everyone writing code should read every page of.

[0] http://www.amazon.com/Cryptography-Engineering-Principles-Pr...