JohnnyRocks - Here is a link to a fantastic simple guide that jswinden created. I use this method because it doesn't mess with the firmware. See the PDF attached to the first post. If you follow the thread, then you'll see from the dialogue that his simple guide was the source of the blog link that you posted. The PDF file also explains when you might need to change the font-family on more than just the body tag and a few methods to do so. Sometimes it is easier to edit the file using the free program called Sigil than to tweak the EPUB in calibre. Hope that helps!