PROS: The ultimate guide in creating a great productivity system. This is the one I started with and it serves as the framework for my entire productivity system.
CONS: Long (352 Pages). Difficult to maintain for some people given how detailed it is. Does not go over when or how to perform certain tasks based on time and energy levels.
PROS: Very short book (80 pages). Focuses on completing your Most Important Tasks (MITs) over shallow tasks. Contains some of the basic Getting Things Done principles. Easier for some people to implement.
CONS: Not a truly complete productivity system however it may be a good one to start out with if you need some motivation.
PROS: Covers how to optimize physical, emotional, mental, and spiritual energy to increase productivity.
CONS: Only focuses on managing energy, not to create a true productivity system. I would use as a supplement to other productivity system books.