You also might be able to do this using some creative compositing-nodes. For instance, the “surface normal” of a surface represents the angle of the face of that surface (as well as its “front side”). You could maybe use that – through a “ramp” node to let you tailor it – to control the emission of a particular color of light. This would give you many of the “outline” details that you see at various parts of the figure … it does not appear that the figure is “solid” at all.
Other details such as those found on the torso might be handled through a texture that is applied to the surface, and heavily filtered.
Compositing nodes allow you to separate the many different digital outputs that the render-engine produces, as well as the so-called “combined” output which is what you normally see. You can string together a set of nodes that do not use the combined-output at all.
I know that nodes now appear in very many places in Blender, including both materials and textures. In fact, it’s reached the point where some folks now speak of: “everything nodes.” They are an extremely powerful and therefore very important aspect of the Blender system. You need to spend a lot of time familiarizing yourself with them, everywhere they are now used. It is essentially a form of “visual computer programming,” which lets you fully take advantage of the fact that you are using a computer.