Ripping myself is what I did with Libation as suggested here. You log into your audible account when starting the software for the first time, your libary is shown and you can start to download.
When adjusting the auto tagging then audiibookshelf automatically sorts the stuff in the correct way with series etc.
Perfect combination and totally free.
I still everyone thinks that boomer`s houses magically built themself and cost nothing. No interest was payed for the loan and the time there where built money rained from the sky.