Yesterday I mentioned my most-recommended article of 2013. My most recommended book was Ray Dalio's "Principles" --
Calling it a "book" doesn't really do it justice. It's sort of a book, but that gives the wrong impression. It has some cohesive threads and themes like a book, but it started as an internal operations manual type document, with a mix of Dalio's high level philosophies, strategies, tactics, and how he ties it all together.
It's rather a remarkable work. Regular readers of the site will no doubt have already seen me having recommended it a bunch already, but if you haven't read it yet, go jump into it.
If the beginning seems a little basic, don't stop -- it's because Dalio makes very few assumptions and begins by sharing his worldview from first principles and the ground up. He builds from some simple and basic concepts into incredible advanced ones very quickly. You'll definitely learn something if you read and reflect on it.