So the window works; it still has to be glued up and have the "glass" put in, but it works. I only had to re-do the decorative framing five times, I think? And the wooden inner frame exploded on me and also had to be re-glued.
The books are still loose, so they are being held together around the inner box by a piece of heavy elastic. The base of the window gives me more than 1 1/2" (4 cm approx.) of display space, which is a good thing, as the inner box is very narrow and doesn't have all that much display space. Now I have to design a small "copper" mansard roof for the window; a friend suggested a potato chip can might help with this, as I would like the little roof to have a bit of a curve to it.
Guess I have to go out and buy some potato chips; too bad, isn't it?