I have now published rough versions of the first three chapters of my book.
A lot of folks have said that Agile is just grounded in common sense. The problem is that common sense isn't that common until you have heard it and applied it. A lot of "common sense" goes against the tugs of human nature. Agile gives you a small number of principles and practices that keep you on the straight and narrow - they stop natural tendencies from pulling you in the wrong direction.
It turns out that a lot of the principles and practices of Agile are not new at all - we just lost track of them by sticking to ivory tower methodologies which looked good in theory but, not surprisingly, didn't actually work in practice.
If we forget the fancy theories, we can turn back to the management classics. These proved themselves time and again in the real world. A great example is the classic books on Time Management, which say "Do the highest priority things first!".
My book relates Agile methodologies back to these classics, and pulls out the essence of why and how they work.
More to come.