I can confirm the same issue. When I click on the icon, nothing happens. When I click on the arrow beside the icon and then choose any Add Book item, it works. Previous versions opened 'Add Book from a single...' when clicking on the icon alone.
Okay, I've just tried it again and I think it's something to do with the click map parameters -- hope that's what it's called
If I click high or in the middle of the icon it doesn't work. When I click lower -- almost on the icon text it works.
Hope that helps.