Installing new fonts for reading fb2 and rtf files is easy:
In your SD card, create a directory named "crengine" with a subdirectory named "fonts".
In /crengine/fonts, copy the ttf files of the font you want to use. It is important that you include all the files of the font. For example, for using verdana, I have verdana.ttf, verdanab.ttf, verdanai.ttf and verdanaz.ttf
Now, if you are reading a book, select "settings" and choose the font you want to use. There are 5 sizes for each font.
Aditionally, in /crengine/fb2.css you can control how the text is displayed (margins, line size, indentation, etc.). In this thread
https://www.mobileread.com/forums/sho...hlight=fb2.css you can find a fb2.css file to play with.
Regards,
L.