This is cool. Our master bedroom has three large walk-in closets. One has double sliding glass mirrors on it and couldn't be anytikng but a closet. The other two have one normal door each, both opening into a larger than normal walk in closet.One is located where it just isn't expected. I am currently using it for non clothing storage.I think it would be fairly easy to make a book case door for it. It wouldn't be a large room but it could hold things I didn't want other to see -- or even all of us for short period.
Thanks for the idea.