I can't remember who recommended me The Ellipsis Manual: analysis and engineering of human behavior, by Chase Hughes, but this is a book every red teamer should read.
This is a highly detailed book on people. Whether you are trying to social engineer someone, or recruit them as part of your insider threat plans, you need to undertand people first.
Mske sure you hsve a pen with you to highlight some of the content, you will find yourself going back to read what you highlighted many times.
Highly recommended