Thank you all for the replies.
most of my ebooks are written in asian language with hell of a lot of glyphs, so the font size is the real issue. with 4-5 fonts alone it already exceeds 20MBs.
on a side note, I use Windows 10 and Sumatrapdf app for reading books.
so my plan is this:
1. save most frequently used fonts in specific folder named, say "epubfonts"
2. remove all embedded fonts in epubs
3. specify the font in css
4. do 2 and 3 in all epub books I am trying to read in that font.
the tricky part is 3, because in this case I have to specify the url of fonts outisde epub file.
for example,
I put all font files in "C:\users\username\document\epubfonts\
and all ebooks in "C:\users\username\document\ebooks\
then what should the relative path be for the @font-face?
for example, the url for embedded font is something like
Code:
@font-face { font-family: "fontname"; src: url(../Fonts/fontname.ttf); }