Quote:
Originally Posted by eschwartz
A dual-MOBI is the default output for Amazon's "KindleGen" converter (used when publishing ebooks on Amazon).
It is also an option in calibre's MOBI Output conversion settings. (You can create an old|new|both MOBI.)
What it means is that the *.mobi file contains both the legacy MOBI content and the newer AZW3 content in one file.
Amazon's PDOC service (and publisher intake channels) only accepts dual-MOBI or old MOBI -- they don't accept pure AZW3 because that means the K1/2/DX and non-updated K3s won't be able to read the book since they only read MOBI.
...
Assuming the uploaded ebook had a cover inside it, and calibre will automatically insert the calibre cover image when converting even if the original file didn't set a cover  then uploading a plain old MOBI *should* show a cover thumbnail.
I just noticed your profile says you have an Android smartphone and are "considering" getting an E-Ink device. 
But I am pretty sure that Kindle for Android works the same way.
Although it absolutely does matter whether you upload to Amazon's PDOC cloud or sideload with calibre -- see this calibre FAQ entry: http://manual.calibre-ebook.com/faq....droid-ipad-etc |
Thank you so much for the excellent explanation of the dual mobi and why it's needed. That makes sense as that they want it to be legacy compatible. It makes me wonder why the newer version (azw3) was actually worth switching to. I'm guessing it had more capabilities within the file itself.
I'm also really grateful you shared that weird Amazon bug with the covers. That's crummy that they set it up that way. I may end up rethinking how much I want to send to Kindle if I have to choose between having my collection either split into two sections (books and personal docs) or losing the beautiful formatting that I've worked hard on. Perhaps having more direct control is going to be more desirable after all and I'll just use the Kindle upload somewhat sparingly.
Again, I cannot thank you enough for your excellent information and helping me actually learn and understand this stuff. I'm so grateful. I really appreciate you sharing your time and expertise.