Best documentary on WWI I've seen. Done in a week-by-week format (300 videos) and in bite size pieces: https://www.youtube.com/playlist?list=PLB2vhKMBjSxMK8YelHj6VS6w3KxuKsMvT
I'll give it a looksy Great book to read if you like it heavy, by Martin Gilbert. I've read it at least 4-5 times. Very informative of the overall situation on all fronts throughout the war.