We did it the other way around, to the other "book" clients: we store the books, themselves, as events on relays, and you can export them from there to PDF, HTML, EPUB, or Asciidoc.
The export function is on the Wikistr client. It's cool because you can download books from relays to your PC or e-reader or whatever.
Here is that Jane Eyre on my Kindle mobile app and my e-paper reader:


