Crown Binding

I figured out this method of bookbinding from a picture. The pages are 'loose', and only held in by a couple of folds of paper from the spine. This means they can 'pop out' and be put back in in a different order or replaced entirely. Fantastic for interactivity.
Could have a story that can be re-arranged and still make sense.
Could have little 3D scenes or fold-out items that pop out to create a world - the book and spine simply act as packaging.