2.0

It's well written, and it is the original GTD-book, but I feel that there are books better suited for today's work environment. This one has far too many sections that aren't that relevant, or are simply anecdotes. It also describes methods of doings things that aren't relevant at all in the digital age - at least for most people.

I recommend "How to be a Productivity Ninja: Worry Less, Achieve More and Love What You Do" by Graham Allcott which I feel describes most of the same processes in a more direct way.