To answer your question, recently two people who have learned Japanese very well over the last few years (in Japan) read the book. They found very many parallels between their own experience and the ideas in "The Third Ear".

I learned Chinese with the approach outlined in the book. Another young man has just spent 12 months in China using the ideas in the book. From a zero base, he is now fluent in Chinese.

During a week in Japan (just last week) I used the method to get started on Japanese. My first goal was initially to be able to just hear separate words in the language, and develop some mastery of half a dozen phrases that were my "toolbox" for switching my brain on to Japanese. A week in, that has been achieved.

In general, the key is to allow yourself to re-access the basic pattern recognition and learning approach that you used when picking up your first language, which I assume in your case was English. Are you going to be learning Japanese in a Japanese language environment? Or, will you be in an English environment with occasional contact with Japanese? The more opportunity you have to immerse yourself, the faster you will learn.

On reading and writing, I have a couple of comments. Initially (for the first few weeks of immersion at least) you want to avoid trying to write or read. This is not absolute, but I find it to be a generally useful guideline. Why? There are a couple off reasons.

Once you can hear most of the sounds of the language relatively well, then you are able to do a one-to-one match of written symbols to audibols (auditory symbols). At that point, learning to read and write is pretty much the same as the first time around.

If you start with written symbols too soon, you risk being too analytical about the whole thing, and you also risk the problem of using the sounds you already know (e.g. in English) and overlaying these on the symbols of your new language. This leads to bad habits, and an accent that can be hard to change later on.