This was cool, of course, but even more interesting was the discussion of education, algebra books, and math teaching that followed in the comments. One thread was the size, cost and general bloat of textbooks, even those for elementary students. Another was the ever changing fads that sweep education.
Education, in the US at least, is a fashion industry. Textbook publishers and their co-conspirators, the education colleges, are always looking for a new gimmick to make the old books (and other media) obsolete. This is actually a bad idea, but I'm not sure how to combat it, short of national education standards.