Wanted to thank Vlad for his efforts in putting this great tool together.
And just to give quick feedback:
I have installed COPS on my NAS (QNAP 439) and all is running fine.
The library also sits on NAS (not in www root though).
Must admit I struggled a bit at the beginning trying to make opds to work in FBReader.
Either I did not find it in the instructions or this is something that should be clear to all, but initially I was pointing Fbreader to the same location as browser "localhost/Calibre_folder". This indeed gave error in fbreader: "...bad opds...".
And only after looking at the code I figured that to access opds you need to use "localhost/Calibre_folder/feed".
Thanks again, and if I can suggest one thing this would be adding "language" section in the very first level of catalog along with "authors", "tags", "series"...
I understand language is visible when you browse through the books, but if I would share the library this would be definitely useful to minimize time of finding something other people will be able to read.