In this and other threads, the idea of a plugin to help _manage_ AudioBooks has been presented.
The idea sounded interesting to me, and so I threw together a Metadata Reader for AudioBooks in the .MP3 format. Very limited for .M4B format.
It is up at http://www.ctc.volant.org/consult/Calibre/index.html
for those interested in trying it (read: testing it for me).
It is still version 0.5.0, so has a ways to go.
But this version I think is stable enough for others to use besides me.
1: multiple files are still separate "books", but are put in the same series
2: still having issues getting the cover image out of the .MP3 file (if present at all).
3: still having issues setting the mi.pubdate and mi.title_sort.
4: no way (yet) to send a books playlist of all chapters to an audio player. ;-)
If you "open" a single book and it will probably play in your OS's normal way.
5: does not write modified metadata back to the MP3 file; it is a Reader plugin.
PS: The default book cover, if I can't find anything else, is a small PNG of an Audio Book.
I am assuming that you are managing a book, as opposed to random music files.