What you want is a default ACL on the top-level directory. Assuming you have a group called "calibre" and a directory called "Calibre Library" you need to set the default ACL to permit access:
Code:
setfacl -d -m group:calibre:rwx "Calibre Library"
This only works for new files/directories created under Calibre Library so you also need to set everything in it once:
Code:
setfacl -R -m group:calibre:rwx "Calibre Library"