I keep forgetting the rules myself, so I should add it to the Readme...
The main chapter names need to be like this: 04-This-Is-The-Fourth-Chapter (the actual file name doesn't really matter)
The chapter name is the level 1 header in the file (single #) - there should be only one level 1 header per chapter!
If we want to separate a chapter into multiple files, the second file should be named 04.1-Sub-Chapter, and not include any level 1 headers (again, the actual file name doesn't matter, only the numbering in the beginning of the name)
There is no practical difference between having one long file for a chapter vs multiple shorter files - the rendered book looks the same (one page per chapter)
I keep forgetting the rules myself, so I should add it to the Readme...