Ask HN: What are the best unknown books you have read?

As for a Sadai's book: it is an extremely thorough book about western harmony from first principles. It treats what is perceived - what we hear - as the anchor, and not what we see when we analyse the notes on paper. A good example of that is how we decide to give names to chords. We tend to name chords based on the notes in them, but this can sometime lead to misunderstandings because the context and how those notes are spread through the chord are also very important. Basics like which note is in the bass is taken into consideration, but otherwise these factors are often ignored. Sadai shows many examples for that throughout the book - as well as such "Mistakes" in other famous books. A quote from the book about the approach taken: "The conventional analytic approach as taught in academies is based primarily upon the depiction of the WRITTEN content of a composition by means of symbols and concepts inherent to the accepted analytic code. This analysis however, which describes mainly what is SEEN, does not always succeed in describing what is HEARD - the perceptual musical essence".

I must have mentally parsed the “unknown” used by OP as “not widely known” (to the HN crowd), and if you look at a lot of the contributions, many of the authors are not exactly “unknown” either.

Only a few hundred people have rated it on GoodReads, but if you wanted to trace a march of technological progress from swords to the Internet, it does a good job. There are definitely other stories you could tell about this accelerating sweep of technological change, but this one was a solid rapid overview and really stuck some ideas with me about how changes compound (or completely swerve to a new goal) over time.

The original tweet is more about how domain experts would rely on books nobody outside that domain has heard of, so maybe I should be thinking more about textbooks that stuck with me. Sources of Chinese Tradition, the Tractatus, and A Mathematical Theory of Computation all left pretty lasting influences in one way or another.

Sources of Japanese Tradition discusses the origins of Tendai Zen Buddhism, with some bits on Dogen, who once wrote something like, "If you want to achieve a certain thing, you must first become a certain person. After becoming a certain person, you no longer want that certain thing."

That's a pretty good tie in to Kessler's view of the last several hundred years of human progress. We were repeatedly solving some other problem, which once we had the tools to solve that, it became nearly irrelevant compared to what else we could do now.