Some books may also contain stuff like the following in their CSS; you can also delete it:
Code:
@font-face {
font-family: "LinLibertineG30";
src: url(../Fonts/LinLibertineG30-Regular.ttf);
font-weight: normal;
font-style: normal;
}
The above was taken from La Leçon d'amour dans un parc.epub uploaded by roger64.
After you delete the @font-face stuff you can then delete the font files that are in the Fonts folder inside the epub.
You'll still need to delete the font-family lines as well.