I skimmed over the project a bit. It seems quite ambitious to aim to reimplement epub, considering that means supporting HTML, CSS, SVG and JavaScript.
Is there a ebook format that isn't just build arround the concept of a webbrowser?
While I agree in terms of modern browser expectations (and books absolutely should not need JavaScript), I think books in HTML makes a lot of sense. HTML was meant for sharing text documents, after all.
Is there a ebook format that isn't just build arround the concept of a webbrowser?