title_body: How to self generate a Kindle ebook with Enhanced Typesetting so that I can left align the text? I generated an HTML page and would like to send it to my Kindle. I'm trying to have this HTML book left-justified in my kindle.
  I used Calibre and Kindle Previewer to generate Mobi, KDP, and HTML files, but the option to left-align the text is disabled in all of them.
  Is it possible to left-align a personal document? Is it possible to generate a book that will be left align?
  If it is possible, which tools should I use and how should I send the book to my device?
upvoted_answer: I managed to have my left-aligned book inside my Kindle, but I warn you that was way harder than I thought.
  You must convert your book to the Amazon proprietary and undocumented format, KFX. This format will allow you to have an ebook with Enhanced Typesetting. Just books with Enhanced Typesetting can be left-aligned.
  Now here are the instructions to have your left-aligned book in a dozen complicated steps. Next year, Amazon will probably have changed its tools and this info will be outdated.
  
  Install the wonderful Calibre
  Install Amazon Kindle Previewer 3. It should be installed in the default location under the same user account as is being used to run calibre.
  In Calibre go to Preferences (the icon may be outside the ribbon) -&gt; Add plugins -&gt; write KFX in the text box -&gt; Select &quot;KFX Output&quot; plugin, right click on it, and install.
  All the magic is made by the KFX Output plugin, here is KFX plugin documentation. Any problem you have in this process, the answer is probably in this thread.
  Now I'm considering that your book is already added to your Calibre library. This is a good moment to check and fix the book metadata.
  Right-click your book and select &quot;convert individually&quot;
  Next dialog, top right, select KFX, run and wait for it to finish.
  Now connect your Kindle to your computer using a USB Cable. No, you can't email your file. You can't use &quot;send to kindle&quot;. You must transfer it using a cable.
  Right-click your book, select send to device, send the specific format to device, select KFX and send it.
  Eject the device.
  
  Now you have your left-aligned book in your Kindle. I don't know if it is worth the trouble.
  If you need to check if your book is correctly converted, rename its extension from kfx to awz8, open it with Kindle Previewer, got To View menu, Book Information and it must have &quot;Enhanced Typesetting&quot; supported: