That’s really nice! We built something in this spirit for automatically transforming a notebook into a HTML report loading some Jinja2 template for the aesthetics (https://github.com/PetitLepton/notebook_to_html_report/blob/df14e3151f9d43cc3c55421bbb1f66716e3df760/notebook_to_html_report/init.py). If only I knew about Jupyter book, it would have been of great help.