Open "Personal Books" tool in a floating window.
Play with resizing the width wider and narrower.
For each width you try, hover over one of the books and see where the Edit/Open buttons show up.
By default they are right justified in the space available. If you make the window wider they get repositioned. But if you make it narrower than a certain width, they begin to get clipped off or even disappear altogether, even when there is still plenty of room for them:
EDIT: It appears it doesn't need to be a floating window. This problem occurs even when PB tool is in a docked tab.
