Hi Boštjan Cigan et al.
I recently installed your plugin onto my wordpress website (v3.8), and it is perfect for what I need. However, I am having issues updating the settings.
When I put the ISBN in (9780713992748) then click "update options", the admin panel loads a blank page. When I go back to see if the options were saved, they were not. This happens no matter what information I put in. The widget loads into the website fine, but, because the options are always blank, nothing appears but the title of the widget.