This is an interesting topic, BoltzmannBrain! I like "meta" too and I might like discussing it even more.
For me, "meta" is usually a "trope" in a work, or a "sub-genre" of a work, rather than the primary genre of a work. Probably most often meta-fiction ends up being a sub-genre of "literary" fiction, although its winks and nods could be applied in nearly any other genre, like fantasy or sci-fi. Meta often ends up overlapping with "magical realism", too, and I think a lot of us might end up using those magical / fantastical labels, rather than calling something "meta".
I don't really know any specific places to go to learn about "meta" I guess. I could maybe name some authors: Paul Auster, Italo Calvino, John Barth, and Milan Kundera all come to mind as literary writers who put that meta-reflective spin on their writing. V. Nabokov and all his games, too.
To me, it's one of the greatest tricks a writer can pull, to suddenly have us looking at the story as an artifact, rather than as a narrative we've let ourselves escape into. When a writer pulls that rug out from you, you stop and say "what? what just happened?" Characters come face to face with authors (like in Vonnegut's *Breakfast of Champions*), books within books within books become the "real" characters, and tons of other fun stuff. It's really really exciting stuff and takes a very deft writing hand.
If we read fiction for those moments that change our perception of our own reality, then meta-fiction does an awesome job of changing our perception of reality by tipping the whole thing on its ear. I love it!
Cheers for making me think these thoughts, BoltzmannBrain!