Typography is ``the art (or craft) of setting type so as to honour the content'' of a text.
Unfortunately, eBook viewing programs are _very_ primitive, using brain-dead / greedy one-line at a time h&j algorithms and _not_ affording much control over appearance --- the limited number of typeface choices is a symptom of this.
Here's an article, which while written regarding the iPad, can pretty much be applied to all other ebook formats:
http://fontfeed.com/archives/ipad-typography/
William