Ned Schwing called me today about another matter so I asked him about the Superposed book and a possible softbound reprint. He had no idea the prices used copies were bringing, wished he had a few hundred in the basement, but doesn't.
He does own the copyright but the plates are old to the point of being obsolete.
Ned talked with a publisher a couple of years back and after pricing it out the publisher figured even a softcover version would be prohibitively expensive.
He doubts he would ever see it reprinted although he always thought it his best book.
I think it an important part of my library and I have all of Schwing's other books as well.