Another movie to look for is Peter Jackson's recent documentary "They Shall Not Grow Old." I wish I had seen it before we toured the WWI sites in northern France. It's remarkable.

The second link leads to one of the best threads ever on Fodor's. The poster, AnselmAdorne, with this thread and a few others evokes the reality of this type of horrible warfare.

https://en.wikipedia.org/wiki/They_Shall_Not_Grow_Old

A Duty Nobly Done — Anselm and Margriet in Flanders and Picardy

Yes, the Peter Jackson documentary played in French cinemas last month even though it was made for the small screen. It is remarkable.

Since Kerouac took his evocative photos of Vimy, a visitors' centre has opened to provide a fair amount of information to place the battles there in context, particularly for Canadians who have come to see Vimy as significant in the country's growth.
At some hours of the day it is possible to tour the tunnels with a guide (who will be a Canadian university student). Both sides used tunnels for surprise attacks. Their opening hours seem to be more restricted than for the memorial itself but well worth planning for.

I agree that everybody says that the tunnel tours are excellent, but I have not been tempted. After doing Viet Cong tunnels in Vietnam and French trenches near Verdun, I think I have fully absorbed the experience. But anybody who has never experienced this sort of thing will immediately understand the horror of war by seeing the conditions where soldiers had to hole up for month after month.

(Anybody who gets a chance to do so should also visit the forts of Douaumont and/or Vaux near Verdun, and you will never want to declare war on anybody.)