I've taken to reading about the first world war lately - my grandfather (mother's side) fought in it after having come to America from Sweden. I recommend this one on the immediate background to the war - Europe's Last Summer. It focuses on the summer leading up to the war, when no one in Europe expected anything to happen. It's a fascinating look at how the continent slid into a catastrophic war. I read that last summer - right now, I'm reading two books that qualify as "oral history" of the war: Eleventh Month, Eleventh Hour, Eleventh Day - it's a view on the end of the war through the eyes of people who were there. It traces back through a number of people's war experience, ending with how they got through (or didn't get through) that last day. Amazingly enough, the allies were launching attacks right through 10:30 AM that day - my grandfather was nearly sent on a suicidal attack that morning himself. Finally, I'm also reading Forgotten Voices of the Great War. It comes out of a British project started in 1972, where recollections of veterans were recorded. It's truly fascinating, from the near ecstasy some of them felt when the war started, straight on to their disillusionment and horror at the front later on. You'll need a strong stomach to read this last book; a lot of the recollections are very, very raw.
I can't pretend that these books give me anything more than a (very) vicarious understanding of what my grandfather experienced, but it's interesting nevertheless. The first world war is the tragedy that created the rest of the 20th century - and the echos are still reverberating through our world now.