Midway upon the journey of our life I found myself within a forest dark, For the straightforward pathway had been lost
This book is intended to explore modern security concepts and acts as a notebook for myself and for others to hopefully learn from. You'll be unlikely to find too many cheat-sheets or dense discussions of the basics of Security, but you'll find more in depth notes on certain key misconfigurations that will likely come in useful down the line.
If you're looking for a straight-forward introduction, then https://xapax.gitbooks.io/security/content/, may make a good resource. In the end this is first and foremost intended as a personal reference, so feel free to suggest things, but the final decision on what is intended will be down to myself.