Hello itimpi,
thanks for your swift reply! Yes, I was talking about the Calibre-folder structure. I was hoping that it is not mandatory for the generated web site of Calibre2opds (it's necessary for the generation, of course - but I was talking about the output).
I've updated to 3.2 today - seems I should also update the German localization

. So in my previous post I was referring to 3.1, where all book pages are re-generated again every time you update/upload. I will give the minimize option a try.
thank you
cyana