Probably anyone who would be interested knows it without its needing to be pointed out, but I mention in case it entices anyone that Gregor Kiczales is one of the authors of "The Art of the Meta-Object Protocol" (https://www.amazon.com/Art-Metaobject-Protocol-Gregor-Kiczal... ; edited to remove abbreviation).
The Common Lisp Object System (CLOS) also uses meta classes; there's a book about it: "The Art of the Meta Object Protocol", http://www.amazon.com/Art-Metabobject-Protocol-Metaobject/dp...
Sadly it seems to be the only approachable resource on meta object systems, apart from a few research papers. If anybody has more literature reference, I'd be happy to learn about them.
Also, inheritance is not a core requirement of OOP. Before you hit that downvote button, consider this: Inheritance allows your class to share attributes and behaviors with another class, and it allows code to recognize that instances of your class have those attributes and behaviors. In other words, when we say "is a", we really mean "does things that match the interface and meaning of". You can accomplish the same thing with "aspects" instead of "inheritance". Following that idea, it is simply a matter of introducing this simple API to add your behavior to an instance:
add_aspect(&foo, 'Some Aspect Identifier'); 