That is probably because most books don't explain it properly. Heck my C++ book doesn't even mention it. And for the extern keyword there is only one very short explanation.
extern: Storage class for objects declared outside the local block. Oh and I read your rant about linkers, ... and it still looks magical. And I bet Andrei's book will keep it short too. And Magic isn't always a bad thing. And the D shared libraries thing, very complex, no magic. C# assemblies. Everything just works, magic.