"Down the rabbit hole." (6.20)
Jace's allusion to Alice in Wonderland proves that Shadowhunters do read books by mundie authors (assuming that Lewis Carroll was actually a mundie), and that he's about to lead Clary into a world that is both similar to her own and radically different.
"Most myths are true, at least in part." (7.29)
Many characters in the book say this line, or a version of it, making Clary's world, with all its vampires, werewolves, faeries, fallen angels, and more, all the more real.
"Dimensions aren't all straight lines, you know. [...] There are dips and folds and nooks and crannies all tucked away." (7.108)
Nooks and crannies, eh? Who knows what magical worlds might exist inside a Thomas' English muffin? So long as they're butter-filled, we're not picky.