My preferred format is ePub and by using OpenInkpot, I do not have the limitations (irritations?) of 9 zoom levels.
Several built-in fonts, margin settings, line spacing, zoom levels, etc. are all available with FBReader, plus a copy/delete functionality. Note that Coolreader3 is also available (not used by me..). PDF format handling is poor but I know they are working to improve it.
Sorry for the Jinke/Hanlin/Astak firmware die-hards ..
