How does the sleep timer work?

The sleep timer is perfect if you want to fall asleep while listening to a book and have it turn off automatically after a certain amount of time. The sleep timer is represented by an icon of a moon with a ring around it. You can find the function on the right side of the player. Press the button and choose how long you want to listen to a book before it turns off. When you press the Play button, the sleep timer starts.