As a manual of geometry and Postscript, the beginning chapters of this book reminds me a lot of my junior school Logo tutorials. But very soon Bill Casselman starts to draw 3D objects in 2D and projection is where the story gets very interesting. (Think how to draw a polyhedron on a piece of paper.)
P.S. One tidbit I learned from this book is that doughnut, oh I mean, torus means cushion in Latin. Hehe.