(Probably)France-only books.
 

Here's a list of them:
U-Boote! Lorient 40-41
U-Boote! Lorient 41-42
U-Boote! Saint-Nazaire
U-Boote! Brest
U-47 volume 1:Scapa Flow's Bull
U-47 volume 2:The survivor
You can look these up,but I doubt there would be even a word of Enlgish in there.
They're full of pictures,and the U-Boote! series also describe every activities in the ports that they describe,the U-47 series are pretty much comics with some Das Boot inspired characters thrown in there,also a bit of U-110(?)in Prien's nightmare,and a documentary at the end.
You can ask me things,as I own them all.