In Championship Behaviours, Hugh McCutcheon provides a pretty comprehensive approach to coaching and athlete development.
Stop Competing and Start Winning is a book about coaching beyond the practices and matches. It's about building and running a program.
The Science of Volleyball Practice Development and Drill Design has some good information based on motor learning concepts, but is a very difficult read.
Coaching Volleyball for Dummies has some good content for new coaches, but a lot of the material when it comes to actual coaching is problematic.
Nikolai Karpol is perhaps best known for his yelling, but that masks a whole lot of coaching success. This book shares his ways of thinking about things.
Dream Like a Champion - Wins, Losses, and Leadership the Nebraska Volleyball Way by Brandon Vogel and John Cook is an interesting view into the mentality of one of today's most successful coaches.
A Fresh Season is Terry Pettit's second coaching related book. Like his first, it's a series of essays and other short pieces covering an array of subjects.
A Program with Purpose by Johan Dulfur is a book that shares insights and experience about volleyball team program building and development