We have begun referring to these as the "sky high" coloring books. That's because the raised outlines of the drawings are the highest we have ever seen. This provides the greatest quantity of tactile input and the greatest deterrent to coloring outside the lines. Wonderfully successful for children with poor coordination, sensory
irregularities and/or low vision. Level one books are simpler with a single object to color. Level 2 pictures are more complex and scene-like.