I've been in love with Emacs and Org Mode for over a decade mostly as a user, only writing basic Elisp in my .emacs initialization file. Writing this book made me even more enamored with Emacs as I learned to write a few packages, and spent much time browsing the Org source code, especially around the export engine [1]. It was useful going through one.el source code as well [2]

[1] https://github.com/emacs-mirror/emacs/blob/master/lisp/org/o... [2] https://github.com/tonyaldon/one.el

And, thank you!