NaturalReader cannot read directly from protected (DRM) ebook files, but if you have a Kindle account, you can use the Chrome extension to read directly from the webpage. Your Kindle library is available to access online through https://read.amazon.com/.
Login to your Kindle account from https://read.amazon.com/
Launch the extension by clicking on NaturalReader's logo from your pinned extensions or selecting NaturalReader from your extension list
Click on any text to being listening or click the play button to begin listening from the start of the webpage