The extended version of the app will contain:

Calendar

The calendar will contain information about which book did user read in given month (when they start to read it and when they finish the given audiobook)

Lock

Lock your screen in you will not want to tap on anything else in the app except play/pause.

Sleep

Set up a time when you want to stop playing an audibook.

Speed-up/Slowdown

Set up a speed of the audiobook.

Extended version will be publish soon on Google Play.
We are planning to extend the extented version of new features. So you can look forward to it!