The book is finished. As usual, I am not happy, so there will be another iteration, this time with design changes based on experience. Usually I'm just speculating. The book, opened out fully, is about three feet long.
Here is a picture looking through the opening.
Sorry the pictures aren't better. I didn't set up properly; since I'm going to do it again, I'll worry about good pictures the next time.
I think this is not a tunnel book in the usual sense. It's really a tunnel, of sorts, but you can't see all the way through it unless you open the folded pages.
I've made several decisions about the overall look:
1. I want one more bridge after the second folded page.
2. I will remove the accordion fold next to the cover, connecting it directly to a folded page. Otherwise the whole thing is too loose.
Above, I clipped the first accordion fold closed.
3. I will be more careful with the outside accordion folds so they will be more closely repetitive, unlike what you see below.
I will change the back end of the book so that it is a closed sheet or another bridge. This is the one thing that needs a decision.
I want to decrease the number of pieces I have to glue. Unfortunately, even though I can print front and back with reasonable registration, some of the pieces have to be doubled in order to have some place to hide the glue tabs. My first thought was to print the bridges on one sheet, but the card stock is not heavy enough to support the other pages. So, each of the six bridges will be doubled, the three larger accordion folds will be double, and small accordion folds will be single.
I made a diagram:
Double lines are glued pages. Single lines with yellow triangles are single accordion folds. Probably makes no sense to anyone else, but I want it as part of my record.
100 Books Before I Die 
Good questions. Yes I think I can increase the depth of field. It requires better lighting and a tripod. Ill do it eventually.
Once I glue the parts it is almost impossible to flatten them. It had to be done upfront. Finally the entire piece compresses easily to about one inch. Eventually, I would like to create some kind of a wrapper to keep it closed. It would be easy to make a separate wrapper, but I would like something that will become part of the book, which requires much more thought. Thanks for your comments and support.
Nope, makes lots of sense to me. It’s really an exciting project. I’m left with a couple of questions that the photo doesn’t answer. Can you capture the depth of field in a shot so you can show us what it really looks like? Is there some way to flatten the glued parts to elliminate the ripple effect? Can you compress the whole piece and not damage it?
Just flat out exciting.
I think it’s stunning! I’ve enjoyed following your progress and thoughts about this project. And, as usual, I’m in awe of your abilities.