The same two documents that ship inside the package, readable here without buying anything first.
Six steps from an empty scene to your first outline — on a mesh and on a sprite. Read this one first — it is short on purpose.
Everything else: the passes, all fifteen styles, hard meshes, cutout, merge groups, skinned meshes, sprites and pixel art, X-Ray layer filtering, the recipes, the scripting API, performance figures and troubleshooting.
Prefer to try before reading? The live WebGL demo runs the full package in your browser — ten chapters, every style, every recipe, meshes, sprites and pixel art, nothing to download. Most questions this manual answers are quicker to answer by clicking.