Open libraries, as well as those where you have to pay for books or membership, do not abound in books or writings on miniature or subminiature format books. Regarding ebooks, this seems to be more the case, as I believe not many have been digitized.
Anyways, see these links here; with a bit of luck, you’ll end up with a good book, downloadable for free. As for the paid ones, well, we all know where to find these, don’t we?
LIBRARY 1 – open library, borrow/read
LIBRARY 2 – contains a list of (almost) every book on Minox and (sub)miniature cameras and photography (not downloadable area)