Finally some good explanation

It says R there. There is even a chapter named "Why R" explaining why R was the choose language for the book.

Very interesting guide. I liked the examples.

The understanding of the author on each subgenre is surprisingly different from mine.

Subgenres in dance music are _extremely_ fluid and change from year to year and even month to month. Some of them are basically just adjective + genre.

The reason dance music has so many sub-genres has to do with how djs mix records. They want to mix songs _smoothly_ and to do that they need songs that sound substantially similar to other songs they want to play. So they find a song or two they like, then they go looking for songs with similar tempos, energy levels, instruments, etc, so they can mix them together. If enough people settle into a particular musical territory, that becomes a "sub-genre", at least for now.

Even something sort of broad like "techno" evolves a lot over time.