Originally Posted by DaleDe
for ePUB the CSS file is inside the file so you can only change it on a per book basis. System fonts can be replaced but not removed. They are in the firmware flash and do not take up user memory. Hopefully at some point Jinke will add support for user fonts on ePUB but today you can change it by editing the ePUB file itself so long as it is not DRM'd.
And how do you break inside to change it?