Right now we get 6 named fonts, 8 point sizes and 3 ways of displaying them (black on white, black on yellow and white on black). That means we have 144 different ways to display eBooks. If one adds to that 24 levels of lighting, that works out to 3,456 combinations of fonts, sizes, colors and lighting.
That should be more than enough for everyone's taste. Remember, the objective is to read more and not play around with the art.
In addition, see this link for a package of SUPPORTED extra fonts for the Kindle Fire HDX:
http://www.amazon.com/Mobile-Systems...=special+fonts
"The font package is compatible with OfficeSuite Viewer and OfficeSuite Professional version 6.10 or higher."
If you use Calibre, it may be possible to convert eBooks to Office format.