They've been mentioning the book sporadically for a while now, I'm relatively new and binged listened so I can't tell you how long ago. As of right now I believe the book is set to drop in February. Here's the Amazon listing for it.
Seriously their research is top notch. They've also got book out that I've been wanting for a while. They also got a weed strain out lol.
Here's the US Amazon link: https://www.amazon.com/gp/product/1328566315
Not available for physical pre-order yet.