On Slackware 13.37 (and maybe other systems as well—probably any system that does not provide udisks), a standard installation of Calibre (that is, installation through the recommended binary installer) does not allow Calibre’s user to access the contents of a connected eBook reader.
To fix this, install udisks (SlackBuild
available for Slackware users), then create a file
/etc/polkit-1/localauthorith/50-local.d/udisks.pkla (the actual
filename does not matter, although PolicyKit developers recommend something
like a reverse DNS notation—the extension however should be
.pkla) with the following contents:
[Access to removable media for the plugdev group] Identity=unix-group:plugdev Action=org.freedesktop.udisks.drive-eject;org.freedesktop.udisks.filesystem-mount ResultAny=yes
That’s it; provided the user belongs to the plugdev group, he should be able to access his eBook reader using Calibre, and to copy eBooks between Calibre and the reader.
For more information about PolicyKit local configuration, refer to pklocalauthority(8).