Is there an overview of the inner workings of the Unreal engine anywhere?

Hey folks. I’ve done my best to google for this, but found nowt.

I’ve started a long-term project using the unreal engine, and I’m likely to be modifying it at a low level. It is a bit daunting to begin with though. For example, I wanted to look at the code relating to matinee, so I searched “matinee” in the source folder, and there were dozens of results from very different places in the folder hierachy. So it’s hard to know where to start.

Does anyone know of a written “overview”, either short or long, of all of the unreal engine code? Or even parts of it? The official documentation has been very useful for me, but that only looks at its capabilities, not how things are implemented.