Yeah... he says you can learn the language in an afternoon, but his book is so long-winded... I just want a short intro so that I can start writing programs.
I really like the conversational style. If I wanted the quickest, driest way to get started in Janet, I'd probably go to https://learnxinyminutes.com/docs/janet/
The book (which I really like so far, 7 chapters in) is more of a deep dive which covers a lot of the gotchas and intricacies without shying away from the nastier parts of the language. The documentation on the official site should get you going in a couple of hours.