Originally Posted by NiLuJe
@walter_2: Make sure the date and time is set properly on your device (ie. sort by 'recent' should be coherent), and that the books you're trying actually have a properly tagged & embedded cover.
Thank you NiLuJe
... that was the solution ...
I think it is a good idea to put this hint into first message of this thread. It is very importend for using cover-mode.