ubuntu 18.04 update problem

I just updated 17.10 to 18.04 which forced a switch from Unity to Gnome. I noticed the top banner now lists at all times one of the books in my library, whether I am using that book or not. I tried opening calibre via terminal and also reinstalling calibre, but that book title now always appears in the top banner. Is there a way to remove it? Best regards, Pop

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