@jagwar,
The method you've just tried will always display the epub in Amasis once you've selected Amasis the first time you open the book, i.e. it will be remembered every time you open it thereafter. This is by far the easiest/fastest method and should work for both DRM'd and non-DRM'd epubs.
The drawback to the above is that Bold and/or Italics may not be displayed correctly. The workaround, if your epub is non-DRM'd, is to edit the .css file inside the epub to use the 4 Amasis font files correctly. The code you need for Amasis is in
post #32 earlier in this thread. Post #80 may also be helpful for outlining ways to edit the css file. You must leave the selected font as 'Original' on the PRST1 for this to work.
If you need more specific help, just ask.