Whenever I had a problem, the Epub book was not built right and had the exact same issues before conversion. PDF doesn't work well, but I don't know anyone does

Whenever I had a problem, the Epub book was not built right and had the exact same issues before conversion. PDF doesn't work well, but I don't know anyone does PDF well on e Reader space Calibre is king, set things right and you can just email books to your Kindle.