Deleting books from the Audible IOS app?
I know this topic is a week old, but I want to add something to the comments already posted here.
The instructions given above for removing audiobooks work, but there is a catch. After an item is removed, it will still appear in the list of books in the Devices tab, even though it is no longer on the device. This is very misleading, and I hope Audible someday updates the app to fix this. As it stands now, you must switch to another tab, such as Cloud, then switch back to the Devices tab. At that point, any items that were removed from the device will be gone from the list.
If you try to remove an audiobook and find that there is no Remove option when you swipe up or down, then the item is probably already removed from the device. Try switching tabs as I just mentioned, and you'll likely find that the item is gone when you return to the Devices tab.