Do not store the library on a NAS
and then try to have calibre open and manage the NAS-attached library. But that isn't to say (and indeed no one has ever said) you cannot sync a mirror of your library to the NAS. As the FAQ points out.
@
ozone123,
Like Dropbox != only Dropbox.
Various syncing tools exist like FreeFileSync/Synctoy for Windows, or rsync for a powerful scripted solution on linux.
Or you can use a Cloud Storage service which, in addition to backing up files online, can sync between devices and a NAS. Dropbox, Copy.com, Box, SpiderOak, there are a whole bunch. Just
don't use Google Drive.
N.B. Avoid FreeFileSync, last I heard the
installer bundles SourceForge Adware.
But FreeFileSync is one of the rare
collaborators. Shame, it was an excellent tool...