Sandreas (Andreas Fuhrich) has developed two tools for audiobook mastering, tagging, and manipulation.

The first is m4b-tool, which is the older but mature tool which will eventually be replaced by tone.

m4b-tool can create an m4b file from a folder of audio files and optionally add metadata, including a cover, description, title, narrated by tag, etc.

Here's how I use it—I put all my audiobook chapters inside a folder, copy the cover.jpg file there too, and copy the description into a description.txt file. Then I run m4b-tool on the directory:

m4b-tool merge "audiobook_dir/" --title="On the Wrong Side of the Crown" --artist="James North" --writer="James North" --year=2024 --output-file "audiobook_dir/audiobook.m4b"

tone can be used to manipulate the tags for audiobook files after they are created. You can dump the tags with:

tone dump input.m4b

You can modify tags or add new tags with:

tone tag input.m4b --meta-narrator "James North"