I would say that the current format is a 'book' in content, but not a 'book' nor an 'e-book' in form, as you can't manipulate it as a single object. But I've seen a few other examples here on HN where people showed off a 'book' purely as a website.
As I shared in a comment above, the book is released under a Creative Commons license that does not authorize sharing derived works so only the original author can distribute you an alternative version