[Katsunami]

Originally Posted by eschwartz

Not a reason to commit yourself to today's implementation of an open-source reverse-engineering of AZW3. (Software always has bugs, and even calibre still gets bugfixes to the AZW3 input plugin. Which are fixes you will miss out on by pretending EPUB is your master format.)

Oh, bother. After extracting the AZW3, or even converting it if the extraction is not to my liking, I run the book through Modify Epub. After that, I run it through the editor, letting it fix errors, fixing the ones remaining myself, and filtering all CSS I don't need or want. Then I fill out the metadata, put in a cover image I like, and run Polish Book.

Now the book is in EPUB, has no errors as far as can be determined at that point, and has metadata which is as perfect/to my liking as humanly possible, as I put it in there myself. Starting from there, I convert the book to the reader I'm using... which in this case, coincidentally, is a Kindle, causing me to end up with an AZW3 again.

I have never had one single problem using this process, and have never encountered even a single error in over 130 books I've read on two different Kindles in the last three years.

(edit: and as long as my master format is as perfect as possible, I couldn't care less what the e-reader uses and how Calibre converts to it. I can always redo that conversion, starting from the EPUB.)

To be honest, I think there is only a negligible chance that these EPUBs or the resulting AZW3's are going to create problems down the line. Sure, if something major happens, I'll return to the original format (which I also always keep, outside of Calibre), and redo the conversion.

There is only one case I've ever encountered, and that was Calibre not being able to convert huge EPUBs (Delphi) to AZW3 without erroring out. I converted them using a command-line Kindlegen script, but when Calibre gained the ability to convert those huge books, I redid the EPUB->AZW3 conversion in Calibre itself.

And not a reason to use EPUB as the source for conversions. Conversions are lossy, and converting from an intermediate format is ill-advised. UNLESS, you have personally ensured the intermediate format is the NEW master format, by manually editing it to fix the problems and making it (more) perfect.[*]And not a reason to start confusing the issue by mentioning KFX.

I have converted/extracted AZW3's into EPUBs that were more perfect than some original EPUBs... I've bought books in EPUB that returned hundreds of warnings and errors in the Calibre editor, while I have also converted/extracted AZW3's that where squeaky clean.

Which is what I am trying to point out.
Always keep the source material.

Don't discard or disregard the source material o ut of some misguided attempt to emotionally elevate "open formats".

Discarding the original source is never a good idea, but converting and fixing/editing the books to one single format is certainly a good idea. A library becomes much easier to manage. As Calibre can handle EPUBs the easiest (some of its tools and plugins even only work on EPUBs), creating an EPUB-only master-library as perfectly as possible is, in my opinion, the best thing to do.