With regard to the podcasts, it would be difficult to overstate their importance and effectiveness in communicating what this approach is all about. They overcome one of the main barriers that text can erect. On the page it can look intimidatingly complex. For instance, if one were to write down all the possible ways to play something as simple as the opening two bars of Indiana, it wouldn't look simple at all. Talk about it instead, illustrating as you go, and everyone can understand without drowning. So it stays simple.
Being a book carries its own problems. Which is where the podcasts come in. It doesn't just sound as if the author is there in the room, the author really is there in the room with the student. And the author has infinite patience, because as often as the student wants he will repeat the lesson word for word, along with the same musical examples. The benefits are enormous. The structured walk-through (to use a phrase once prevalent in my computing past) which the podcasts provide means not only that the song is understood in depth - probably for the first time - but that the key it is to be played in is irrelevant. Understand it once from the roadmap/podcast combination, and you understand it in all keys. But the song is not seen in isolation, and this is the other huge benefit they confer. They set the song in its historical context, mentioning recorded versions and discussing approaches, and they also set it squarely within the territory which comprises the whole of the standard repertoire, by means of references to other songs which use identical or similar devices.
I'd say the podcasts are the most significant event in Harmony with LEGO Bricks since I published my original book in the mid eighties.