If you set a sleep timer you will easily find your way back even if you happen to fall asleep while listening. To set the sleep timer, open your book in the Player and click on the moon symbol (you can find it on the far left above the cover picture). Choose for how long you want the audiobook to play before stopping.
If the book stops and you want to continue to listen, you can either click on Restart (to reset the timer), Shut off (to turn the sleep timer off completely) or you can jump back to where you first set the sleep timer.
If you find a place in a book extra interesting, and want to be able to find your way back to it later, you can add a manual bookmark and include a note.
To add your bookmark, open your book in the Player in the app and click on the bookmark symbol.
Manual bookmarks can also be useful if you switch a lot between different devices and want to make sure you can continue to read or listen from where you last stopped.
Do you want to slow things down while listening, or speed it up? If you open the Player in the app and click on the 1.0x symbol, you can choose which speed you want to listen to.
The different settings are 0.75x of the standard speed (slowing it down), 1.25x, 1.5x, 1.75x or 2.0x.