Converting html to boustrophedon styled html

To convert html file to boustrophedon writting style, download boustrophedon.js, then add to the end of html file this line:

<script src="boustrophedon.js"></script>

Converting epub to single html file

You can achieve that using pandoc and running:

pandoc -f epub -t html -o ebook.html ./ebook.epub --self-contained

Step 1: Resize browser (firefox) window to A4 dimensions in pixels:

Step 2: Open html file in the custom viewport window and wait until everything is fully loaded in the browser

Step 3: Save loaded html file to PDF:

Press Ctrl + P
In the "Print..." window set paper size to A4 and select "Fit to page width" option
You can change here margins and unselect "Print headers and footers"
Click "Save" button

Notes:

you don't need to use exactly A4 dimensions, it is just my suggestion
if the letters are too small or too big or you want to just add more styles, you can add your styles to html file (see: boustrophedon.css)
you can treat txt file as html file simply by changing file extension to .html