There's also
Lucidor, which can be installed as a Firefox add-on (not compatible with ePubReader) or standalone (works better).
The ePub you should try to get an idea of just what the format is capable of is the version of Jerome K. Jerome's comedic classic,
Three Men in a Boat, done by one of our very own MR moderators. Looks absolutely marvelous as-is, turns to rubbish once converted to mobi.