Some of Norton's Witchworld books are available on the darknet, as are many others that the publishers haven't published as ebooks.
If the book is important, it will survive. Even if it's obscure we have Project Gutenberg busily producing ebooks from some of the most obscure books I've seen.
And if you want to help, you can always sign up with
Distrubuted Proofreaders and help Project Gutenberg add more books.
Current Books in Proofreading Round 1.