title_body: Is there a compelling reason to distribute both '.azw' and '.mobi' files? I am currently researching what ebook formats I should be targeting. I would like maximum distribution potential with minimum fuss (for both myself and users, with the latter taking priority). I have noticed that some sites provide both .azw and .mobi files while others opt for one or the other. According to Wikipedia, Amazon's file format offering is just a lightly modified version of the Mobipocket format. I also know from my own Kindle usage that I have never had a problem using Mobipocket files on it. I also believe there are other readers that can handle this format but not Amazon's native one.
  
  Is there is any advantage to providing .azw or .kf8 formatted content if I am making .mobi files available anyway? Would this just me added clutter to my interface and product offerings or would is there something to be gained from the extra format? I will be making .epub and perhaps other formats as well so this question is just about the best way to support Kindle readership.
upvoted_answer: .azw is basically .mobi with the possibility to add DRM. According to the wikipedia article you cited it even has less instead of more features. Since using DRM is kind of pointless if you also offer a DRM free .mobi version, there is no advantage.
  
  .kf8 supports some HTML5 and CSS3 features which the other formats don't. This allows creating more advanced layouts which may be an advantage if you have more than just plain text with chapter marks and headings.