The app is designed specially for playing audio books.
Assumed that you have audiobooks and already copied them to your phone.
First 30 days Full version. Later - Basic version.
Features:
+ Chromecast support.
+ Playback speed control.
+ Classification of books (new, started, finished).
+ Download cover from the Internet.
+ List of characters. You can manually create a list of characters to easier follow the story.
+ Automatic pause in case you fall asleep. To continue playback just shake your phone.
+ Playback history.
+ Application Widget. Allows you to control the player from the home screen.
+ By specifying a root folder containing all your audiobook, you can exclude your folders which contains music and other audio files.
+ You don't have to finish one book to start another. The progress is saved independently for all books.
+ NO ADS!

To purchase (restore after reinstalling) full version press:
menu--Help--Version tab
Phone must be connected to the Internet.
Full version cost is $2.

Many thanks to people who left comments and suggestions.
If you have something that doesn't work please write an email instead of leaving a comment.

Version for Android 4.4 - 5.1:
https://drive.google.com/file/d/159WJmKi_t9vx8er0lzTGtQTfB7Aagw2o

Version for Android 4.1 - 4.3:
https://drive.google.com/file/d/1QtMJF64iQQcybkUTndicuSOoHbpUUS-f/view?usp=sharing

Version with old icon:
https://drive.google.com/open?id=1lDjGmqhgSB3qFsLR7oCxweHjnOLLERRZ

Recent changes:
+ Fixed situation when pressing outside of Add/Edit Bookmark/Character dialog leads to dialog closing and losing all changes.
Now to close these dialogs you must press OK or Cancel button.

+ Long press on Big rewind or Big fast forward button makes very big rewind (x10).

+ Added Sleep timer schedule:
Settings--Sleep--Schedule.

Now you can set the time for the sleep timer to start and stop.
You no longer need to turn it on every evening and turn it off every morning.