I had the impression that his book was rather anecdotal, an interesting overview perhaps, but not finally so deeply engaged with the music itself or the technical issues 20th century composers faced to achieve sincere self-expression.
I'm sure you already know this, but only the walzer of Op 23 is actually 12-tone. One of the things that makes the set so interesting is that it was probably intentionally written as a history of his development of the 12-tone technique. Of course, they are all serial (for the most part, although there are interesting exceptions within the movements), and of increasingly rigorous technique up to the walzer. It is almost a transition from the expressionism of Erwartung and Op 11/19 etc to the more restrained, in a sense classical Op 25, which I think he began writing while finishing 23.
Your dismay with the common dismissals of these masterpieces as experiments I wholeheartedly share. Perhaps part of the problem here is also the fact they have been so championed as analytical examples for composition students and not so much by real musicians. I fall into this danger myself constantly, as I find the analysis fascinating, and in fact I made some videos showing some basic motivic and formal analysis on top of Pina's playing, but she asked me to take them off, and perhaps she is right. It would be good to allow Schoenberg to stir the imagination for awhile instead of just the intellect.
The commodotization of music is another huge concern for me (also, as a kind of unfortunate contradiction, from the viewpoint of someone who wants to make a living from it), and of course, as Adorno I think very convincingly argues, was at least partially the sort of pressure that shaped Schoenberg's development. The fact it is possible to argue over whether Op. 23 is too visceral, as it seems to be for Ross, or on the other hand equanimous as you feel I think is intriguing and very telling. His music tends to become more and more expressionistic, and in this sense human, yet more and more structured and rigidified. The increasing amount of control ceded to technique and precompositional decisions is almost oppressive to the expressivity of the material - I think the 4th movement is an extremely good example of this. It's hard to breath afterwards. Even the forms of these pieces share in this paradox, having one form that is heard and one that is functional and structural underneath.
And so one can't help but feel the human drama of the music, at once immediate and subjective, and at the same time feel alienated by that same very high pitch of subjective expression to the point that the piece becomes objectified. This process of personal alienation through objectification, if I can use that as a word, is one of the major themes of the 20th century, and is I think in large part why this music is so pertinant and beautiful. And if it was an experiment, it was certainly successful. The fact that it is not so readily marketable is in this sense precisely the point, and it is the perfect antidote to the pop, commercial, "brand" culture that in my view pervades and generally doesn't help even the classical field.
But perhaps these things are slowly changing. I think there is a chance his music will be reappraised and reach significantly larger audiences sometime in the near future. It is starting to receive more concerts and more sensative performances. Of course, Op. 11's atonality turned 100 years old this year, if I remember right, so it's about time!