Traces the history of geometrically 'impossible objects' from the impossible tribar pictured on the cover, through the Penroses' article on ever-ascending staircases, through to Escher as beyond, with some psychological explanation of how the eye tries to understand the images.
Most of the brain-hurting pictures are just the same as in Adventures with Impossible Figures, but there's more text and history. The overlapping material includes how to make a 'real' 3D tribar -- by building a model with a gap in it that is invisible when viewed from a particular direction. But here we also get to see much more impresive gapped 3D models of Escher's famous "Belvedere" and "Waterfall". And there is a fascinating snippet at the end of how to build these impossible objects without gaps, but instead with curved members; this time it is the curves that dissappear at the critical viewing angle.