While I am in a book, not the library, if I tap in the lower quarter of the page I get a pop up showing percentage of book read as well as the page number in the current chapter.
In settings under Look & Control, I have Hide status bar checked and Show Page Numbers checked. But, I've played around with these settings and I don't see that they change anything. If I uncheck Hide Status Bar it will still auto hide just as it does if I leave it checked. There are actually 2 status bars. One you get by tapping in the middle of the page. That show some controls. The other is the one I already mentioned, by tapping in the lower quarter I get book progress and pg#/pg total of the chapter.
