[jhowell]

Unfortunately Amazon has been going in the direction of becoming increasingly proprietary with each of their ebook formats.

MOBI was based on HTML 3 and the propriety packaging was actually fairly standard for the Palm platform that it first appeared on.

KF8 is a lot like EPUB 2, but with the ZIP package replaced by something more like the Palm database used by MOBI. Proprietary but with standard underpinnings. Converting KF8 to EPUB is more a matter of repackaging than rebuilding.

And now with KFX Amazon has gone in a far more propriety direction, eliminating HTML as the basis of the format. Apparently being different mainly for the sake of making conversion difficult. Added to that KFX comes with a new, more effective, DRM scheme that they quickly took steps to improve when it was broken recently.

Added: In fairness I think the goal in making KFX not based on HTML was increased rendering efficiency in low powered devices, and that difficulty in conversion was just an added bonus from their point of view.