Suppose someone had published a several hundred page (sensitive) book, but had randomized all of the letters in an order known only to them (e.g. with a vector of random numbers of the same length as the book's characters).
This initially strikes me as relatively riskier than something of comparable simplicity (like a one time pad) since the letters are all in the clear. But, I can't quite see how an attacker would benefit much from that information. Are there known attacks on this sort of thing to learn things about the text? What could be learned? Could one maybe at least tease out an idea of what the book was about? At what message lengths (if not all) could it be a big problem?
Hopefully this doesn't qualify as asking the community for "peer review of a cryptographic scheme"!