Postmodernism is an artistic movement that defies definition, but it is largely concerned with the abandonment of objectivism, rationalism and other ideals embraced in past movements and periods such as the Enlightenment. Many themes and tendencies arise from postmodernist thinking. A common literary device used in postmodern literature is metafiction, in which the artificiality or creation of the text is incorporated into the text itself; in other words, literature that is self-conscious. Metafiction is prevalent in contemporary memoirs, which often feature the author speaking from a first-person perspective, speaking directly to the reader and/or referring to the written text itself.
Post-structuralism can be most simply defined as the linguistic aspect of postmodernism. It is concerned with both writer and reader perspectives, claiming that a written text lives beyond the author once it is part of the literary canon, and that a reader's subjective reality is a large part of the textual meaning experienced. This translates into more specific tendencies, such as a conscious objection to conventional textual structure and/or typography. Many post-structural themes deal with the abstract nature of human interaction, especially in the context of written communication.
Subjectivity is a theme that plays into both postmodernism and post-structuralism. However, subjectivity itself often plays a large role in 21st-century literature. Many contemporary texts embrace subjectivity by incorporating multiple narrators or perspectives throughout the story. It is also common to find literary works that embrace wildly different perspectives, in an aim to force the reader to establish a subjective reading of the entire text. These themes primarily stem from the postmodernist tendency to reject objective truths or perspectives.
The Information Age is defined by the explosion of computer and Internet technology over recent decades, which has allowed for an exponential increase in the exchange of information. Themes in 21st-century literature that come out of this include continued themes from the cyberpunk movement, which often feature dystopian societies that have been overrun or destroyed by technology. A continuance of existential themes popular in postmodernist literature can be seen in 21st-century literature, applied to the digital world of computers and online identities.