Aftermath - The Remnants of War by Donovan Webster[1] is highly recommended and has a section on Zone Rouge.

[1]: https://www.amazon.com/Aftermath-Remnants-Landmines-Warfare-...

There's a great book about this phenomena, "Aftermath: The Remnants of War." Apparently unexploded ordinance in Europe from WWI is very common because trench warfare lasted for years and, due to relatively primitive manufacturing techniques, mortars, bombs, etc. often failed to detonate. That explains a lot of the comments below about French farmers getting killed by ancient munitions

https://www.amazon.com/Aftermath-Remnants-Landmines-Warfare-...