The Elements of Pop-Up
This book for "aspiring paper engineers" provides an encyclopedia of pop-up effects each with explanation of how it works. The more complicated effects which benefit from a model that can be disassembled are not glued shut allowing the reader to open them up to reveal the inner workings. The opening page has a very dramatic monster which serves to illustrate many of the techniques combined for a single creation. The ending page gives an overview of the steps to publish a pop-up book.
I've found this helpful in designing pop-up cards, which I make as one-offs.