To me it's the perfect mix: simple voice, simple & compelling imagery, just enough accompaniment. What is the song about? I have no idea, but that's exactly the point: It's little mystery that you get something more out of every time you listen to it -- like all great songs.
The important elements of the lyrics --
It resembles another favorite song of mine, "Hotel California" by the Eagles. What is the song about? Who the hell knows, but the imagery is so compelling that we try to figure it out every time. The song work and lasts forever because the mystery is both compelling and unsolvable. (The last thing we would want is for the songwriter to tell us what he was thinking when he wrote it; that would totally spoil the illusion.)
Sobule's song, I imagine, started with the words "Houdini's Box" and was built from there. It doesn't really have to "say" anything; it just has to leave you with haunting questions.
The ending is perfect, the way it leaves you hanging.
I've tried listening to Jill Sobule's other songs, but none can compare to this. The others, I think, get too wordy and specific; they don't remain lyrical and symbolic like this one. She's got a fantastically subtle voice, but she's just not putting it to good use.
What she needs is a good concept editor.