Adding bookmarks, notes, and highlights in an audiobook

To add a bookmark: Tap bookmark icon at the top of the audiobook player.

To add a highlight: Play the audiobook, then tap and hold bookmark icon to highlight a passage. 

To add a note to a bookmark or highlight: Tap bookmarks and notes icon, select a bookmark or highlight, and tap bookmark icon. Then, make a note, and tap Save.

Bookmarks, notes, and highlights are saved in the audiobook under bookmarks and notes icon (and reappear there if you borrow the book again).