Michael Mandelbaum's book, recommended by CL - a quick review because I didn't really think it was all that fantastic. The central hypothesis is that peace (or a preference for peace over war), democracy, and free markets are the cultural ideas that have come to the forefront over the last few centuries. He therefore paints the past conflicts - especially the world wars and the end of the Cold War - as a triumph of these ideas over their opposites.
It's an engaging theme but a little too simplified I think - and the simplifications required to make the argument work in the end make me more distrustful of the conclusion. Okay to read, kind of dry, and seriously - much of this stuff is old news.