I just got a copy of the 3rd-edition of Hacking for Dummies by Kevin Beaver.
I read the first edition about 6 years ago. That edition was great, with its clear, easy-to-read style that won't intimidate readers unfamiliar with abstruse security terms and concepts. This edition seems even better.
This edition is broader, but like the original, it shows the reader all of the steps involved; from the basics of security to the hardening of an operating system and the hacking of Web applications.
Should be a very good read.