I payed $15 for a booklet. It's overpriced. I didn't say the content was bad, but that $15 is too much for what you get.
Pico8 games are also coded in Lua, as are several other game development environments. At the moment there are more resources for Pico8 than Playdate, so it makes sense for people to get practice within Pico8 then carry that over to playdate - if they want to. If someone has no interest in Pico8 then they can ignore my advice.
Mboffins videos, tutorials etc, aren't more visual they are more practical, you learn by doing, and there is a lot of it, and I payed for it because its high quality stuff. Squidgod's booklet is about Lua coding in general, it's more technical. Practicality and tinkering are very important for beginners, since knowledge forms out of experience from the specific to the general. Print() code, or it's equivalent in other languages, whether its cout or something else, won't cut it if you want to figure out how the machine is running and build machines of your own. And, I almost forgot to mention, the help from AI is huge, it's explanations and examples are extremely helpful.