The book Messy, by Tim Harford, is a book that explores the value in not always being neat, orderly, and well-structured.
The Brain Always Wins by John Sullivan and Chris Parker could be quite beneficial to both your coaching and your own personal health and development.
Peak - Secrets from the New Science of Expertise helps you understand what the concept of deliberate practice means and how to apply it.
Barking Up the Wrong Tree by Eric Barker is an interesting combination of stories and research that could help you both personally and as a coach.
Great Teams is a book that does a really good job combining sports and business insights into a resource with a lot of good concepts and ideas.