In the past few months I've read a couple of works of metafiction. I've probably read books like this before, but I'm more aware of them now than I've ever been before. I think they're fascinating. Last year I read Michael Ende's The Neverending Story, in which the book itself plays a key role - and the narrator of part of the book turn out to be one of the characters. Those two facts are very intertwined, and are part of what makes the book more interesting than a regular children's fantasy adventure (not that there's anything wrong with those!)
I also read Jasper Fforde's The Eyre Affair. Fforde's novel has characters slipping in and out of their real world and the world of Jane Eyre. I'm not sure if it's actually metafiction, since the focus is more on different realities than on layers of fiction, but it's certainly something very similar.
Just recently, I finished reading Life of Pi by Yann Martel. This is the book that sent me on my quest to find out more--I got to the end of the novel and was confused, but intrigued. A little bit of research brought up the topic of metafiction. I don't think it specifically helps me to understand the novel better, but it gives me a context to place it in. It's also opened up a whole new world to explore.
I think Terry Pratchett's Witches Abroad, which I've loved for years, might be metafiction too--it certainly deals with the concept of metanarrative, which is somehow connected. The cherry on the top is that my current Bible reading notes are subtitled 'Adventures in the Biblical Metanarrative'! I'm going to be looking out for the concept from now on and trying to figure out more of what it actually is.