title_body: How do I download DRM-free books from Amazon? In a previous question, When shopping for ebooks on Amazon how do I
  tell if they have DRM?, it is explained that DRM-free ebooks on Amazon
  are characterized by the "Product Details" item: "Simultaneous Device
  Usage: Unlimited".
  
  I was a bit surprised though that all such books I looked at also had:
  "Lending: Not Enabled", which seems a bit contradictory. But this is a
  side remark.
  
  My problem is that I do not know how to download these (supposedly DRM-free) ebooks, once
  acquired.
  
  I did go to my Amazon page "Manage Your Content and Devices", where all my Amazon
  books are listed, one book on each line.
  
  There, it seem that to download a book. I must click it in the Action
  column (the second square of the line), and then select an action,
  which apparently should be "Download &amp; transfer via USB".
  
  But when I do, I get an error:
  
  Download &amp; transfer via USB
  Select a device from the dropdown 
  
              John - Android Tablet
              John's Kindle Cloud Reader
  
  You have selected content that is not compatible with any of your registered 
  devices. Please remove incompatible content from selection for eligible devices
  to appear.
  Transfer Tip: After downloading, use your USB cable to connect your computer and
  Kindle. Your Kindle will appear as a drive on your computer. Copy your downloaded
  file from your computer to your Kindle's documents folder.
  
  
  All I want is to get the MOBI file in my computer, as I do with other ebook sellers for DRM-free books.
  
  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.
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.