This was a fascinating and wonderful read. As someone who also works on tools for thought, here's my review and criticisms. The material is long so this will be longish too.

Review

The bulk of the essay is on what the authors refer to as "the mnemonic medium". A mnemonic medium, of which they use their work, Quantum Country, as a motivating case-study is an essay format which embeds flash cards containing carefully constructed questions and combines them with spaced-repetition to improve recall of the presented material.

The authors argue very convincingly that memory is an important and undervalued aspect of expertise. Much of the initial struggle in learners is from a lack of basic fluency in the vocabulary of an area. They show, including with supporting data from the aforementioned work, that this significantly increases recall of material (nearly all if the reviews were done properly). Even if you want creativity and think you can just look things up as needed, having the material readily available in memory will serve as a potent catalyst to one's creativity. The over-head is reasonable, they estimate 4 hours to read the material and ~100 minutes of spaced review to achieve months or more of retention on material.

They talk about the more typical sense of mnemonics, such as the method of loci and memory palaces. Such methods they argue, do not generalize well to different learning domains, especially more abstract areas.

They also point out the weaknesses of their method. Including requiring general motivation, a reason to learn the material and difficulty of crafting good atomic connected questions. Finally, they discuss why not much progress has been made in the area (funding of public goods problem), other mediums such as video and the executable book/notebook format and what inspirations can be drawn from video-games interface-wise and art generally from an evocative and emotional perspective.

Criticism

The simplest criticism is if the results will generalize. The topic matter on the technical aspects of quantum computing has already selected for a probably uncommon sort of person.

It is the authors' stated goal that they produce a method with broad applicability. Although they spend some time on the weaknesses of their approach, they could have spent a bit more on nearby failures. Engelbart had a bootstrap program, where each set of tools propelled us to ever more powerful augmentations. One major problem Engelbart found was that once people reached proficiency at one level, they had no interest in further gains. The complexity of peripherals has gone down over time (from multibutton mice and chorded keyboards to pointing with fingers) and people simply were not interested in learning complex peripherals. Some discussion of the difficulties faced by http://witheve.com/ at getting something with broad applicability and lessons from it would have been informative.

There is much work to be done in ending the dumb users trope and also in educating people that many things worth doing will be difficult. Engelbart often pointed (he was against voice as a primary control) out that you can't talk your way down a ski-slope yet people are happy to learn the difficult task of skiing. How to get that engagement generally?

The next major criticism is the difficulty of content creation. Writing a text is already difficult but writing one that is clear and with carefully crafted embedded questions will be much more difficult again. We can see hints of this in the quite low publishing rate of the Distill publication where a large aspect of the low rate is due to the difficulty of content creation. We are still several generations out from tools which ease the creation of interactive and tasteful (where interactivity is actually illuminating rather than a distraction as is often the case) executable notebooks.

The authors mention differential geometry as an example. Such texts are difficult not only from subject matter but also because they are often presented in a user hostile manner. With key information, including on notation, left out. This has been fine historically because these books are meant to be used in a supporting environment with lecturers and assistants. However, learning these autodidactically adds in an immense artificial layer of difficulty from ambiguity. It seems like an obvious thing but material written in a clear manner with no external support needed is already rare. Going beyond that will be a tall ask.

The fairly self-contained aspect of quantum computing might not transfer to differential geometry. To do that properly, one would also need to have material for adjacent topics such as multilinear algebra, differential forms, calculus of variations (for some motivating problems), analysis and some topology. That is a very large stack to get through and can be quite discouraging for the learner even with the dream of near perfect recall. The time investment might scale differently too and might require more of a fraction of study time.

For the creators, by the time you get to multimedia, and the need to do this is an accessible (accessible to blind, deaf, etc) manner, an already difficult task becomes nearly unmanageable. Perhaps, narrow AI tools (the authors do point this out too but also see Rainbows End by Vinge for a fictional take on this) will ease some of this but basic UX and API design for interactive education will also be pivotal and are sorely lacking. I do not believe the authors sufficiently acknowledge this.

The authors seem to make the mistake that experts will be the best authors of such media. I am skeptical of this. Very few experts maintain the empathy required to communicate with novices. I suspect the best approach and this is hinted at by the author with their example of Norvig's notebook, is someone either with exceptional empathy or who has just mastered the material, recording notes for themselves and then sharing. But it will take a while yet before such tools are in place.

Finally, the authors also discuss BCIs. Their examples of new modes of thought suffer from the same criticisms they have for the Logo programming language and creating properly motivated and connected questions, perhaps worse. From what little we know, this will not be just a matter of interfacing with visual areas but also with broad wide reaching networks in the intraparietal sulcus, inferior temporal cortex, angular gyrus, hippocampus and frontal areas just for a start. These are all involved in complex problem solving and will differ in detail from person to person. How to get a non-superficial interface beyond super low latency I/O is a great challenge and simply beyond the horizon of what is today imagineable.

This is as long as I'd feared it would be but I hope someone finds it useful.