I've just released audible-api v0.6.4, which fixes the two issues you've reported:
- Prevent use of empty
SERIES-PARTinALBUMSORTandCONTENTGROUP. - Prevent
ARTISTto start with comma if onlyNARRATORis provided.
Thank you for sharing the regular expressions. I've not incorporated any of those mainly based on your words of caution from above.