It's an oval shape, the frame highly ornamented, and while it only floats about two feet off the ground, it's a good five feet tall. Which makes the image reflected in it quite clear. You won't see yourself or the library in it, but rather another room entirely. Trying to touch it at all will make it quickly apparent this is a sort of portal to the world it shows.

The boy doesn't look directly at it, but he doesn't have anything to say about it, he just looks upset.