Originally Posted by GMFuller
I've seen the same thing with azw files (not sure about the traceback but I'm sure I've seen the "BadZipfile: File is not a zip file" message)
I assumed it was because the book needed to be in epub format, so I converted the book and counted pages on the converted file.
It does seem odd that the plugin says there's statistics to be updated rather than saying the ebook format needs to be different.
Converting isn't a good idea. You do change the number of pages because you change the code. So the page number you get on the converted eBook is not the same as the source eBook.