title_body: Can custom fonts be embedded in mobi or epub books targeting eink readers?
upvoted_answer: You can definitely embed fonts, yes. There are a few issues to watch out for when doing so, however:
  
  
  You may not have a license to use the font in ebooks. The font needs to be licensed in such a way as to not just allow use, but also distribution. There are a number of open source fonts available that do permit redistribution--make sure you read the license, though, before using any of them. Many of them will also require that the license be included; it's easy enough to just throw that into the font's directory, but be sure to actually do it if the license requires it.
  Many reading systems (I'm looking at you, Nook) will by default override publisher CSS and use their own instead. If you use fonts as the sole differentiator for different types of information, you'll lose that info when publisher CSS is turned off. If you're using a different font in place of bold for emphasis, consider markup up the text as &lt;b class="exclamation"&gt; ... &lt;/b&gt; instead of &lt;span class="exclamation"&gt; ... &lt;/span&gt;. Then you can define b.exclamation { Font-weight: normal; font-family: awesome_font; } in your CSS. That will make the text bold if publisher CSS is off, but put it in your awesome font if publisher CSS is working.