Well clearly it would be a good idea to enable the user to specify the location of the books. If that was implemented, the user could choose a location in say, Dropbox, and thus sync books between Macs.
It seems inconsiderate to dump the books folder in the root of the home directory. Normally an app would choose its own Application Support folder location, or at least a folder inside the Documents folder.
Is there no option or command that can move the location?