The whole book is already out: https://nostarch.com/art-mac-malware

It's a great read :)

Volume I is out (and available at that link), but the main page has a place holder for Volume II: https://taomm.org/index.html

Curious if he has indicated more about it in any of his presentations etc.

He also has a great youtube channel where he posts devlog type stuff: https://www.youtube.com/c/devaslife