Adding cover image (or editing metadata) to audiobooks in Mac OS Catalina

Hi. I couldn't reply to the previous questions about adding book covers and editing metadata.

I recently needed to change a few things on an M4B book. I soon realized I couldn't do anything with them using the Books app on the Mac, and obviously not on the Music app. I have this app on the Mac that I've been using for a while to change tags on MP3 files and decided to try and use that.

Lo and behold, I was able to change the album cover and edit some metadata. If you need to do something similar, it's worth a shot.

Here's a link to the app website with download and installation instructions.