Jupyter Book 2 is build upon the MyST-MD document engine. This serves a very similar purpose to the Sphinx documentation engine that was used by Jupyter Book 1. However, MyST-MD is designed from the ground-up for technical and scientific writing, and provides some exciting features such as rabbit-hole links.
To minimize the complexity of integrating two separate software product, the jupyter book binary is a thin “shim” around the MyST-MD CLI, i.e. Jupyter Book 2 is MyST-MD (bundled with a default Jupyter Book configuration)! We firmly believe that the right choices for the MyST-MD CLI are the right choices for Jupyter Book. To help make MyST-MD feel more like Jupyter Book, we set a few environment variables that superficially change its appearance. Consequently, power users can use the MyST-MD CLI directly!
Jupyter Book 2 is MyST-MD [...]; power users can use the MyST-MD CLI directly!
We made this choice to recognise the different starting points of the existing Jupyter Book and growing MyST-MD communities. By keeping the distinction between Jupyter Book and MyST-MD as small as possible, we can ensure the mutual growth of both projects.