Hello there, lgoldberg.
Although this content is written for purchased Audiobooks from the iTunes Store, the recommended steps for deleting on your computer still apply:
How to delete content you've downloaded from the iTunes Store, App Store, iBooks Store, or Mac App Store
http://support.apple.com/kb/HT5772
iPhone or iPod touch
You can't delete an audiobook directly from your iPhone or iPod touch. But you can delete one by syncing to a computer with iTunes, then following the instructions for Mac or PC below.
Make sure you back up the audiobook. You will need to purchase it again if you want to download it.
Mac or PC
Before you delete, back up the audiobook. You will need to purchase it again if you want to download it.
- Open iTunes.
- From the Library pop-up menu, choose Books.
- Click Audiobooks in the navigation bar.
- Click the audiobook you want to delete.
- Press Delete on your keyboard.
Thanks for reaching out to Apple Support Communities.
Cheers,
Pedro.