Accordion Book with Jacob's Ladder Binding

A simple proof of concept. I've seen other accordion books, but not any with a binding that keeps the covers together while opening both ways. (There are plenty that bind the whole book as Jacob's Ladder, ie. each page is separate.)

 

You could use a simpler arrangement, but having the string go through holes keeps it together better. Notice that the crossing strings must go to the very edge of the covers or there will be too much slack to close the book properly. The pages too must be full width — or slightly wider to accommodate for the width of the strings between opened covers — so you can open the book flat.