If you aren’t familiar with TV Tropes–(you’ve really been missing out)–it is sort of like Wikipedia, except it deals in tropes: recurring elements in (mostly) works of fiction. The site describes a trope as something that “[conveys] a concept to the audience without needing to spell out all the details”. The TV part of its name is really a misnomer (or, per the site’s terminology, an Artifact Title), because it touches on movies, books, video games, comics, mythology and religion, and even historical events.
A few examples of tropes from the page for ‘House of Leaves’ are ‘Beast in the Maze’ (the Minotaur), ‘Hooker with a Heart of Gold’ (Thumper), ‘Lysistrata Gambit’ (when Karen won’t have sex with Navidson), and ‘Painting the Medium’ (use of colors throughout). There is a (if you’re unfamiliar with the site, that is) surprisingly sophisticated discussion of the book’s unconventions, as well as the speculation that Danielewski might just be messing with all of us. The page is probably a more user-friendly and inviting introduction to Postmodern lit than anything else I can think of.
Think about what you learned in English class–plot, characters, style, word choice, symbolism, whatever. TV Tropes covers it all surprisingly well (except grammar/punctuation, but thoughts on that will come later), while also being free, fun, relevant, and a really easy way to waste hours of your life.