I listened to that series about a month ago. I had no idea WW1 was so 17'ing horrific.
What I knew about WWI before that series was Franz Ferdinand, The Black Hand, All Quiet on the Western Front, Legends of the Fall, and Galipoli. Now, all I can think about is the Schlieffen Plan.
If y'all liked that HH series you should check out The Great War youtube channel. They did an episode every week for 4 and 1/2 years , from 2014 -2018, detailing what happened that week exactly 100 years prior. It's broken down into entertaining and informative digestible chunks.