David Allen is a productivity guru. I first came across the GTD methodology from the bob.blog and then was further exposed to the ninjary by Merlin Mann at 43folders. Ready for Anything is divided up into 52 short chapters and it can be viewed as the why behind all of the GTD methodology. It is full of reminders as to why we need to get things out of our heads, why we need to review our stuff weekly, and the freedom to be creative that we establish when our brain is able to focus on one thing at a time.
If you have already read Getting Things Done this is a great addition, to understanding the processes and methods of GTD. Be careful though as David Allen has created a cult-like following among many in the blog-o-verse. But it’s a great resource and you should check it out.