[NiLuJe]

@KarlSchroeder: You must be referring to a Topaz book. There is absolutely no way to change the font(s) of these books without external format-shifting. (And I wouldn't really recommend doing this, given the nature of the Topaz format, it's slightly more tedious to do than usual, and you'll likely end up with something worse unless you know what you're doing/how to fix it).

Fortunately, only a handful of books are provided by Amazon in this (potentially horrible) format.