The book is published on https://xpqz.github.io/learnapl 
or as a single pdf https://github.com/xpqz/learnapl/blob/main/contents/_build/pdf/book.pdf

GitHub repository to report comments, issues, etc.: https://github.com/xpqz/learnapl

Links to references made during the presentation:
- Advent of Code: https://adventofcode.com/
- APL Orchard:    https://apl.chat
- Link:           https://github.com/Dyalog/link

John Scholes' "A Plea for Simplicity": https://youtu.be/qSVR4Z3DA24