FBI wanted criminal and the world most known hacker, Kevin Mitnick, writes an exceptional manual on social engineering.
The book is divided into stories, each one full of tips and tricks on how to play misconceived trust to obtain information for the hack in question.
The security chain is as strong as its weakest link. I personally think the human factor of the IT Governance will always be the entry point for the most destructive exploits.
This book can help you understand the importance of personnel role on the security, or lack of it, in the enterprise global IT security plan.