The Practical Step-by-Step Guide to Making Pop-Ups & Novelty Cards: A how-to guide to the art of paper engineering, featuring over 100 techniques and ... 1000 fantastic photographs and illustrations
Fun ideas here. Cool way of presenting new ideas: first outlines a new mechanic, then has a page with an idea using that mechanic. A little lacking occasionally in discussing the theory of a particular mechanic, e.g. the construction of hubs is difficult to see in detail.