Originally Posted by RobertJSawyer
qlob, it looks to me, in limited testing, that Amazon is now serving ALL books -- new titles and old -- in AZW3 format. Titles I'd previously downloaded let me change justification, but even old books seem now to be being delivered in the AZW3 format (or, at least, their sample chapters are).
For a different reason, I've been doing a mobi-to-mobi conversion in Calibre, so that newer mobi files can be read by my older Cybook, etc. If you set the Calibre option to save a mobi conversion in the old format, you might be able to get back your justification option.
If you do, post and let us know.