@horusofoz - I'll try to answer your questions as far as how this plug-in currently works. If there is a reasonable way I can extend it to do what you want, I am not against extending the plug-in. First the current behavior:
re: manage audio books without making them part of a series
Calibre is designed so that one file == one book
. The problem with Audio Books is that typically Many files == One book
. There seems no reasonable way to change this concept in Calibre - it would make things unnecessarily complicated for every book that wasn't an audio book, I think. And make Calibre unnecessarily complicated to have two different and competing philosophies in its internals.
re: Are there other ways to "bundle" Audio Book Chapters besides the "Series" column.
Yes, there are two (and a half) other way I considered.
1: create a custom column for the "book" that the chapters belonged to.
2: merge all the MP3 files into a single MP3 file to give to calibre.
2.5: merge all the MP3 files into a ZIP file to give to calibre.
I didn't choose #1 because there is more work to creating a custom column, writing all the UI parts and tweaks to make using the custom column trivial, etc. It was simply easier for _me_ to use the series column, for which all was already written. ( At the time I hadn't thought about audio books also being part of a real series. )
I didn't choose #2 because it makes for one huge MP3 file, and that was a reason it was broken into chapters in the first place. It seemed a lot of work for no good benefit to glue them back together.
I didn't choose #2.5 because it seemed I didn't need to write a plugin at all if that was the route one was going to take. Calibre is perfectly capable of managing ZIP files, though it doesn't try to get metadata out of them.
re: OK, so what about when I have text and audio of the same book
I really have no good solution to this; though I am open to ideas.
What I do is keep my text books and audio books in separate libraries. I personally don't ever happen to work with both at the same time. ( I realize that might not work for your situation. )
re: what about the future?
I am current toying around with the idea of:
* a plugin (or tool) that converts a collection of audio book files into an EPUB file
This is essentially a fancy #2.5. A tiny HTML file is created presenting all the gathered metadata and linking to the various chapter files. All these files are "zipped" into an EPUB file, which Calibre already knows how to handle.
I was thinking of using a different extension than EPUB even though the structure is identical just so Calibre would let you put them both as alternate formats to the same "book".
* I am also awaiting to see what will really come from EPUB v3 file format which is capably of combining text and audio into the same EPUB file.
If that becomes usable in Calibre, then that might be a better format to "convert" audio books into.
(: and being naturally lazy, I don't want to write the converter twice.
If you have ideas that might be workable, we can discuss them.