Schwaber, K., and M. Beedle. 2001. Agile Software Development with Scrum. Upper Saddle River, NJ: Prentice Hall. Tucked away in the last chapter of this book are the Scrum values. Reading the clear and compelling definitions of these values is mandatory for any agile coach. Reading them several times over a period of time, and considering them carefully, is mandatory for any great agile coach.
Pink, D. 2009. The Surprising Science of Motivation. http://blog.ted.com/2009/08/the_surprising.php. Want to know what matters to people and what this has to do with why they would reach for high performance? Watch this short talk to find out. If you want more, get his book Drive: The Surprising Truth About What Motivates Us, which goes deeper.