We publish our work on The Future of Text in PDF because PDF is a frozen and non-interactive medium–with a few exceptions–and this is for the long haul, an archival journey. The web is great but links break over time. We want the book to be robustly available for the long haul and we believe that PDF documents will be kept readable for a very long time since it’s such a pervasive format.
We have develop an open metadata standard called Visual-Meta which works with PDF to allow the documents to be richly interactive. You can read more at https://visual-meta.info if you like. We have also developed the macOS Author word processor and the Reader PDF viewer. If you use Reader to read The Future of Text, your reading experience will be augmented in how you can navigate and interact. Reader is free:
Other formats of the books will also be available from the download pages.