Speaking of Good Books ...
Another good book, with only an indirect connection with GTD. is Daniel Kahnemann's Thinking Fast and Slow. I read it a few months ago after having picked it up almost by accident at an airport bookshop with a very limited selection. I did not expect much, but it proved to be one of the best books (for me, that is) that I have read in a very long time.
It also deals with something very old and almost obvious, but from a fresh and neutral angle and with lots of factual support. I think we have all probably experienced the inner conflict between "heart" and "mind" sometimes - where our emotions or intuition drives us in one direction and our analytical or logical component drives us in another.
This conflict has "always" been recognized - it is and age-old conflict, and many of the common descriptions are simply ludicrous. For example, I was particularly disappointed by the intelligent writer Mark Forster's term "the lizard brain" (for the intuitive part) and the adjoining description of it as "slothful, reactive" etc. That's not my view at all - how can people even get such an idea! And in religions (in most creeds, probably) there is the same denigration of the "flesh" as opposed to the noble "spirit".
What Kahnemann puts forward is a simple model for how the mind (brain) can be described as if it were two interacting systems (nothing new so far - that's how they all describe it) where one of these represents the more "automatic" and the other the more "reflective" thinking (nothing new there either). What he does, that is new - at least I have never read it in a book before, but normal people often seem to be aware of it - is that none of these two "systems" is perfect. Your reflective self makes errors that the automatic self would never do, and vice versa. They both have their strengths and weaknesses, and most of the book is dedicated to establishing a number of types of mistakes, biases and delusions, where either system tends to trump or mislead the other, and demonstrating these cases with experimentally proven results. He's a professional psychologist, Nobel prize winner in Economics; with lots of "data" to support his case.
The connection with GTD is not very direct at all - mainly that even in task management you need to use both your reflective skills and your intuitive skills, for example how to organize and label your stuff versus how to make the final pick of tasks to do.