Format AZW3 is file format created for eBooks – electronic books. It was developed by Amazon especially for Amazon Kindle service. It was called KF8 or KindleFire8. To open these files we can use Kindle for Windows or Kindle Reader for Mac OS.
Main advantages is ability to use HTML, CSS, you can create comics and last but not least he adds lots of fonts. He also adds 150 various options to format text, page counting or sidebars. As last we should rite that he supports vector graphics.
Best known program to view these files is Kindle Previewer, which is distributed by Amazon on its own. You can download it for Windows or Mac.