I've been reading Carl Von Clausewitz's On War. It's a tough read, since it's written first as a book about the analysis of war, then about war itself. This means that those looking for Clausewitz's views on war will be initially frustrated. Because of this, I'd only recommend the book to a serious fan of history or war.
The book is essentially the only real attempt to make a universal, comprehensive summation of war. (In comparison, Sun Tzu's Art of War is more like a brief meditation on the subject of war.) I've been wondering why there isn't a modern version today. There is no comprehensive guidebook to modern warfare, so far as I know.
"Modern Warfare" is a difficult term. The most recent war the USA has been involved in is the Korean War. Since then, American troops haven't had the chance to exert their true power. I believe that there will be a return to "traditional" war in this century, (that is, tank movements across a countryside, artillery destruction of whole cities, and two large nations bringing their complete strength to bear against each other) and no one knows how it's going to happen. I can guarantee it won't look a whole lot like World War Two, though.
Now playing: David Bowie - Space Oddity