This is super cool! I actually have been working on a new book recommendation site (https://braincandy.com) that has a similar-ish (but much smaller scale) visualization for book similarity. It is really interesting how certain genres tend to be much more insular than others and it can be a real challenge to break out of genre boxes when making recommendations. There's so many books out there on the edges and in-betweens that get lost when they don't fit neatly into an existing popular genre, and those indeed can be some of the most interesting.