A slightly different book about the Great War that I really enjoyed was "The Last of the Doughboys" by Richard Rubin. Over like an 8 or 10 year period he traveled all over interviewing those who fought in the war. Some didn't want to talk about it, some didn't want to stop talking. Some had mental capacity that prevented the interview from amounting to much. Or died before he could meet with them. They are all over 100 years of age. I found it interesting, their stories. The last one, Frank Buckles, died in 2011. The insight was amazing. I wish I had thought of interviewing guys like that. My grandfather died 9 years before I was born, so I never got to hear his stories.
A guy I met on the 100 anniversary Doughboy tour gave me a digital copy of his grandfather's diary that he kept throughout the war. Our grandfathers were both in the 32nd division, his in the artillery and mine in the infantry. We took a picture of us both standing under the sign coming into Romagne where our grandads had both been. His military life wasn't anything like what I imagined it was like.
Sounds as if you have a deep interest in that war. I cannot emphasize enough, if you haven't already, that you should take a tour to France and Belgium and stand in places where it all happened. You will never forget it. I just need to go again!