[foldedcornice]

This is an interesting quote, though Keller's response appears to be framed in the context of business and/or self-help books: more explicitly, books Keller read "for interest," rather than books about technical subjects.

His response (immediately before much of your quote) was: "They spend all this time highlighting and analyzing. I read for interest, right? What I really remember is that people have to write 250-page books, because that's like a publisher rule. It doesn't matter if you have 50 pages of ideas, or 500, but you can tell pretty fast. I've read some really good books that are only 50 pages, because that's all they had. You can also read 50 pages, and you think, ‘wow, it's really great!’, but then the next 50 pages is the same shit. Then you realize it’s just been fleshed out – at that point I wish they just published a shorter book."

That doesn't sound like books that take more effort to really understand (e.g. Plato's works). In more technical subjects, such as mathematics textbooks, would it really be possible for most students to thoroughly understand the subject by just reading, without note-taking or at the very least, trying the practice problems? There is certainly value in note-taking for subjects and books worth thoroughly understanding, even accounting for edge cases where students can learn complex subjects just by reading, without writing.