It basically states calibre, cloud, web browser, Kindle apps, email, USB.
Here you have a list of different ways to load books on your kindle, probably one of those will allow you to extract the book itself.Downgrade your Kindle software, as someone said in another answer.Use Kindle Collection Manager to browse through your books, but it's pretty old, I don't know if it will work on modern devices.Install Calibre and check if it allows you to import the book from the Kindle to your computer, in which case you'll have the files available directly in your hard drive, inside the library folder.There are some things you could try, though:
First of all, Kindle file structure has evolved over time, so if we don't know your software and kindle's version it's quite hard to give you a more precise answer.