Besides the pop-ups, the illustrations have a very nice line quality that I admire. The paper engineering was done by Clare and Jack Segnit and Dennis K. Meyer.
I hate to give away the ending of the book, but the pop-up on the final spread is so nice I couldn't resist showing it! It's very simple but also elegant and effective.
The photo doesn't completely do it justice - take a look at this book if you get a chance!