More about Project Gutenberg: http://gutenberg.org
Not the entire book. I wouldn't have to copyleft the entire thing, right?
My current static page is just an "I like this book, please give me this free thing and put me on a mailing list" kind of thing. But that's not really the point. The point is "how can I use static pages, presumably the thing the internet was built for, to put a few pages of extra material on the book and perhaps give links for folks to follow if they're interested in the topic?"
Traditionally, you'd issue a new edition with such information, but that seems like a hella work and expenditure, and small stuff like this should be the kind of thing you'd be able to stick somewhere online, if nothing else as a parking spot until you eventually publish a new edition.
I wonder if the Internet Archive would be interested in this kind of archival.
Unfortunately, with the recent attack, the purl.org resolver went offline and remains so. All the purl data is still there and is accessible to the public, you just don't get resolvable URLs for them.
Nowadays, it seems like ARKs are the better way to go, anyway, and the attack on archive.org proved it perfectly. Look into <https://arks.org/>
(The Internet Archive mints ARKs for every item uploaded to its collections. You may have noticed them in the infobox below the fold when looking at a given item.)
As for your latter remarks, the Internet Archive will take just about anything. Create an account and start uploading. Ted Nelson has a huge chunk of his papers on there.
Possibly even some useful legitimate fodder for those fashionable AI data sinks!