Very recently I came across this book: La super-artillerie allemande à Verdun. Looks like a great read. I have ordered it, but it seems my local book shop has trouble tracking it down...
No, I have had no dealings with them, so definately no problems. It is the payment part in an foreign country that often is a problem, as I do not have a credit card anymore. I did sponsor some criminals for 700 euro´s once, and for me that was quite enough...