Here is an extract from The Cambridge Companion to Literature And The Posthuman that I liked:
“So, postmodernist literature, criticism, and theory - one of the main characteristics of the "postmodern" is that these three discourses can no longer be distinguished - often give the impression that it is a kind of waiting for an impossible event (the "new" or unexpected other), while writing goes on and endlessly produces fiction, which writes about the (im)possibility of writing the event. There is a kind of performativity and circularity, sometimes even an apocalypticism that seeks to invoke, con- jure up and somehow express the ineffable. This is also the reason why intertextuality, or the notion of the intertext, can be seen as one of the central presuppositions of many postmodernist theories and practices. Every text is not only an open system but is also never identical to itself. It is part of a system of textual relations, a form of generalized textuality which alone guarantees the readability of our cultural universe. Thus intertextuality is the very condition of perceiving social reality and there- fore has quasi-ontological status. This also explains the proliferation of narratives about narratives, the fragmentation and loss, the dissemination of identities and the critique of the "unified self" in postmodernist writing. In a textual world where every fiction is only another text, metafictionality becomes virtually interchangeable with intertextuality. As Patricia Waugh explains, metafiction is "a term given to fictional writing which self-consciously and systematically draws attention to its status as an artefact in order to pose questions about the relationship between fiction and reality."
In postmodernist fiction, both metafictionality and intertextuality are employed to demonstrate the constructed (or fictional) nature of human reality. In so doing, postmodernist metafiction serves an important "pedagogical" purpose in helping to understand contemporary ideas about reality, which can take a variety of negative and positive reactions: from experiencing the idea of general textuality as a "prisonhouse of language" to the "new forms of the fantastic, fabulatory extravaganzas” in magic realism (Salman Rushdie, Gabriel García Márquez, Clive Sinclair, Graham Swift, D. M. Thomas, John Irving). The generalized notion of textuality thus often leads to a celebration of the power of fiction and fictionalization seen as equivalent to a reality- or world-building process. Some of the most frequent framing devices to be found in postmodernist metafiction thus include "stories within stories, characters reading about their own fictional lives, self-consuming worlds or mutually contradictory situations, Chinese-box structures," thus reaching the conclusion that there "is ultimately no distinction between 'framed' and 'unframed.' There are only levels of form. There is ultimately only content perhaps, but it will never be discovered in a 'natural' unframed state."
