Horne's writing is delicate, elaborate, and sweeping. He lavishly paints a picture of the events leading up to Verdun and the battle itself, highlighting the major players in command and tracking the nightmare on the front lines. I always knew Verdun as a “meat grinder” and while that's true, there are distinct beats to this 10 month long battle and I came away with a more nuanced understanding of them.
The author depicts the flow of battle with expertise, and illustrates the effects it had on both sides. He dives into the nightmare of the new weaponry introduced at Verdun, like flamethrowers or phosgene gas - and you can almost feel the panic as your own heart starts racing imagining what it must have been like to confront these terrors.
I have only two criticisms of the book. Horne will sometimes reference a “well known” figure without giving any context. If you don't happen to know what person or their backstory, it's up to you to figure it out. He will also regularly cite quotes in French (less often German) without any translation, so you'll need to have at least a basic understanding of the language if you want to understand these, or run them through a translator.
Regardless, this stands as one of the best books I've read on WWI and I highly recommend it.