As in Booknizer you can organize not only paper and electronic, but also audio books, there is a built-in audio player in the program. It will play audio book files directly in the program. All most popular audio book formats are supported.
The track list of an audio book is shown on the book's page. To start playing a track, just click its title:
The controls of the built-in player can be found at the top of the main window, next to the menu items:
Here you can switch to the previous or next track, rewind the current track, stop playing altogether, or select a track from the list of the current audio book (to do so, click the arrow next to the play button). On the right, there is a volume control button.
Besides the built-in player, Booknizer is capable of using any media player installed in your system.