Principles of Information Security 4th Edition (PDF)
Product Review (submitted on March 22, 2017):
If you have the opportunity to read this book while not enrolled in college, you'll appreciated it even more! The first four chapters might not be your cup of tea if you just care about firewalls, IDS, IDPS, VPNs, and encryption, but if you are a scholar and interested in security principles as a whole, get this book. Get the Kindle version if you can. I have the paper back and I wish I had the digital version, too!