Favorites

I have a book open on my iPad.  I want to put it into a favorite.  I click the three vertical button and select 'add to Favorites'.  It gives me no choice as to which folder in my favorites to put the book.  I then go three parallel lines or bottom right, tip it, then it shows my favorite folders but I don't see where the book was added even after I look in each folder. 

Should I not be given a choice as to the folder to put the book.  And currently which folder is the book placed?