Covers every area of "systems" security you can think of and quite a few others that never occured to you. Thought provoking to say the least.
Ever wondered how banks transfer cash transactions, how credit cards and PINs "work"? It's all here, described in some detail along with the errors and pitfalls encountered along the way.
If you are "in to" secure systems then this book provides the sort of background you need to start thinking the right way about systems engineering.
Nuff said.

I found Ross Anderson's seminal book on Security Engineering surprisingly readable considering I have a fairly non-technical background.

Covering everything from pay-as-you-go electricity meters through tachographs to military and banking systems, the book gives a superb introduction to the real-life challenges faced in the security world and an insight into how easy it is for even the experts to get things wrong and fail to anticipate how a system will be compromised.

Ross Anderson's home page includes the contents, sample chapters and errata : http://www.cl.cam.ac.uk/~rja14/book.html