title_body: How do I download DRM-free books from Amazon?
upvoted_answer: Simultaneous Device Usage: Unlimited is not a reliable indicator of DRM-free books. AFAIK, all free Public Domain books sold by Amazon Digital Services are DRM-protected.
  
  For example, this free Amazon book is listed as Simultaneous Device Usage: Unlimited, however it's not DRM-free. 
  
  
    I am running Linux, if that can be any help. But I do not own a
    Kindle, and my only devices are my PC (running Calibre on Linux) and
    an Android pad used by another person.
  
  
  In that case you can easily test for yourself whether a book is DRM-protected:
  
  
  Install the Kindle for PC app via Wine or Winetricks and register the app with Amazon by entering your logon credentials.
  Send the book to your Kindle for PC app via Manage Your Content and Devices and open it.
  Open a terminal window and enter the following command to locate the Kindle books folder:
  
  cd ~/Documents/My\ Kindle\ Content
  Right-click the .azw file and select Open with Calibre.
  If Calibre doesn't display a DRM warning the book is not DRM-protected.