I have a kindle version of a Clay Sanskrit Library book, "The Five Discourses on Worldly Wisdom" but its not possible to zoom in on the text.  Is this the case for all the kindle versions of Clay Sanskrit Library books?

  I use kindle on Windows and I have other kindle books (not from the Clay library), some of those I can zoom and even if I can't zoom I can change the font size to increase the size of the text.  But neither of these methods work for the Clay Library books.

Harry Spier