I had a post up earlier today that linked to a Munsey’s Technosnarl post that claimed Amazon’s TPZ file format for eBooks was an ePub variant. (I didn’t see the retraction, posted later!)
That turns out not to be true at all.
This is a post by the guy who created TPZ for Amazon: Interesting Topaz DRM development (geekery, job stuff)
It has absolutely no relationship to any other ebook format out there; it is not “mobipocket with fonts,” it is not “a proprietary implementation of ePub,” or any of the other ridiculous things I’ve seen written about it from people who have no idea but make these statements as if factual
The short version: TOPAZ is a series of scans formatted in such a way to provide reflow. I suppose something along the lines of reflowable PDFs now available.
It’s a very interesting post that should be read by every Kindle owner.
I think it’d be very rare to come across an eBook aimed at the mass market in TPZ format. It seems it was created for special formatting cases.
Mike Cane’s xBlog 
Hmm, just got a Book on Leonardo from AMZ, and it’s in TPZ file… right away you notice the beautiful graphical fonts (very different from bland AMZ files).
Oh well, I guess it’s kinda funky for more graphical texts (its a book on Leonardo, there should be lots of great imagery).