When taught in January at MIT, a highlight was something I'd not seen elsewhere: someone called it the "aftermath" (3-pun). After the one-hour traditional-ish lecture (on video), the room was reserved for an additional hour.
When previously taught, people would remain afterwards to ask questions, discuss math, and chat. So this was an iterative-improvement formalization of that.
People would gather in front of the blackboards in fluid discussion clusters. Catalyzed by the three instructors and wizzy others, not all having to stay for the entire hour, but drifting off as discussion died away. They could show material they had pruned from the lecture, for want of time. Or got dropped as they ran over. Alternate presentation approaches they had considered, before selecting another. They could be much more interactive. One commented roughly "If I was tutoring someone, I'd never present the material this way". It was a delightful mix of catching the speaker after a talk to ask questions, a professor's office hours, a math major's lounge, an after-talk social, tutoring, an active-learning inverted classroom, hanging out with neighbors in front of the hallway blackboard, chalk clattering and cellphones clicking to snag key insights... It was very very nifty.
So, the book is nice. And lecture notes. And videos. But... the best part isn't there. Perhaps the next iterative improvement is to capture the aftermath on video, and share that too.
And as we look ahead, planning distance-learning and XR tools... maybe something like this is a vision to aspire too. The insane ratio of expertise to people learning is not something one can plausibly replicate in meatspace. But as conversations in front a virtual blackboard gradually become technically feasible, something like this might pay for the cost of it, with transformative impact.