I just finished read "All Quiet on the Western Front" that is about WWI trench warfare from a German soldier's side. It's really quite depressing and eye opening. The conditions these kids went through were insane. Toward the end of the war it was basically untrained, hungry, poorly armed kids (18 years old) that were just sent to the front lines to basically get mowed down.
Though WWII gets most of the attention, I think WWI was ultimately the more important of the two historically. A complex system of alliances between the great powers set into force a series of events that turned a Balkan assassination into a global war. Serb rebels attacked Austria, which attacked Serbia, which dragged Russia and Germany in, which activated the Schliffen plan, which led to the attack on Belgium, which brought France and the UK into the fight.
It was a war based on sheer stubborness, one that never should have happened had Russia and Germany ignored their alliances. This led to millions of men being mowed down, millions more injured both mentally and physically. They gave the best years of their lives so aristocrats could have an international pissing match. Then when all was said and done, the aristocrats told them to basically f-off. So these soldiers began searching out radical alternatives. In Russia, they turned to a man named Vladamir Lenin and his Bolsheveks. In Italy, a nationalist looking to restore the nation to its former pride and glory became president; Benito Mussolini. In Germany, a young soldier and artist named Adolf Hitler was outraged that his nation was forced to take sole blame for the war, and blamed it on a Jewish conspiracy. He joined the DAP party, became leader, then chancellor, and led the world in another bloody conflict more barbaric than the last.
From here we get the WWII, the holocaust, the cold war, and the current conflict in the Middle East. History is like a web. All events, past and present, are interconected. WWI served as the catalyst for ideas and conflicts that created the modern world. It's a shame it tends to get ignored in classrooms, reserved for one day a year.