Cryptography Engineering

I would recommend Schneier's Cryptography Engineering (or its predecessor) Practical Cryptography over Applied Cryptography, given the question. I agree Applied Cryptography is a very interesting book, but that's because I'm a crypto nerd. For someone looking to improve general software engineering skills, I think the other books do a better job of presenting best practices and the understanding behind them, with a bit less mathematical theory, etc.

- Managing the Professional Service Firm by David Maister - Quantum Computing since Democritus by Scott Aaronson - Cryptography Engineering by Bruce Schneier et al - Time Management for System Administrators by Thomas Limoncelli - Expert C Programming by Peter van der Linden