I'll check it out, but the new AAX2MP3 does allow you to change the names of each "chapter". You just have to know what it is you want to change it to. I don't like it to just show "chapter 1" when it's playing, so I experimented with a novella changed the descriptions to "series" - "title" - ch01 (02, 03, etc.) and that worked. A bit manual - not sure for some of my that have 70-80 chapters I'd want to do it that way.
But I'll search for mp3tag to see how that works. Anything to make the process easier - I have *lots* of Audible audiobooks that I'd like to liberate.