Here is Jen Fox’s recommended reading list from her Moscow Rules talk:

Advanced Interviewing Techniques: Proven Strategies for Law Enforcement, Military, and Security Personnel. John R. Schafer and Joe Navarro. 2010, Charles C. Thomas. [I got a lot out of this book. It approaches from a different angle than most of us will in our jobs, and because of that covers some different territory than other books.]

Confidential: Uncover your competitors’ top business secrets legally and quickly—and protect your own. John Nolan. 1999, Harper Collins Publishers [This book is out of print, unfortunately. A very informative read about information elicitation techniques.]

It’s Not All About “Me”: The Top Ten Techniques for Building Quick Rapport with Anyone. Robin Dreeke. 2011, Robin K. Dreeke. [Straightforward book about ten techniques for building rapport. I would say this book is a great starting point on this reading list.]

Learning From Strangers: The Art and Method of Qualitative Interview Studies. Robert S. Weiss. 1994, The Free Press. [A book from the sociology discipline, where there is extensive experience in interviewing/observing for information gathering.]

Please Understand Me II. David Keirsey. 1998, Prometheus Nemesis Books. [As a Myers-Briggs nerd, this is my go-to reference for MBTI personality typing info. I’ve been using this as a reference for years. Excellent for dealing with bosses, coworkers, significant others, kids.]

The Definitive Book of Body Language. Allan and Barbara Pease. 2006, Bantam Books. [Good book; there are also a number of others to choose from on the topic of body language. I understand Joe Navarro’s books are good.]