This is my first time reading On War, and I have to say that I am so far impressed with the relative ease with which Clausewitz can be applied to modern situations. Book I serves us well not only as an overview of the entire work, but also provides the reader with good baselines, defining fundamental concepts with simple language and examples that I presume would make it possible for the completely uninitiated to understand.
What I find most fascinating though is the high level of Clausewitzian thought found in Marine Corps culture, and I would guess (hope) to some extent in the cultures of other US services as well. I am not certain whether this is by conscious intent, or rather a coincidental development stemming from the Corps’ history and role, but several examples were immediately obvious to me as I read.