Microsoft Encyclopedia of SecuityJust got a copy of the new MS Press Encyclopedia of Security by Mitch Tulloch. Mitch also maintains an interesting technical Blog at Blogspot.
This book is a good A-Z reference guide to all the key security issues likely to face any IT Pro. It's not a definitive look, by any means, with around 1000 entries in some 480 pages. But it is a good basic intro to all the key terms. It even covers .NET security concepts such code access policies which is good. The level of depth is not great - but there is a good introduction provided with some references for more information.
If you have to understand more about security - and let's face it, most IT Pros need this understanding, this book is worth buying!