Personally I just bought a mid-year textbook on cyber security from the University of Waterloo and I'm making my way through it. It's surprising how bad cyber security is, but so much of it is right there in the pages of this book. It's like finding out you can buy a Patriot missile for $250 and some spare time in the evenings.

edit: And of course this book would be unapproachable had it not been for the work I've done in engineering, software development, and machine learning.