Sorry its an old issue, but i think it may be useful for others who will found this page.
With the same installation note, i cannot use calibre in opensuse 42.2. It starts in background and says "calibre is already running". Also there is no calibre-gui.desktop file or else to start calibre -only related desktop starter files such as calibre-lrfreader.desktop, etc.
I solved the problem by starting calibre from terminal by the command:
LC_CTYPE=C calibre
I think it is about the language settings.
reference in Turkish:
https://forum.ubuntu-tr.net/index.php?topic=53731.0