Updates: All the Mobipocket reference books I have installed so far work fine except for the Oxford Dictionary of English. If anyone has any hints about how to get that working please share. In the Launcher folder it is simply ignored. If I try and install manually I get the error 0x30060209.

Another hint: Garnet is not optified, which means it will take up valuable space in /usr/bin. However you can optify it manually using the following commands in terminal (install rootsh first if you haven't already):

sudo gainroot
mv /usr/bin/gvm /opt
ln -s /opt/gvm /usr/bin/gvm