Symbolism, Imagery, Allegory
The Cheesiest
Velveeta sandwiches don't stand in for the unnaturalness of Midwest life or for Libby trying to find a substitute for healthy behavior. (Or do they?) We just have to mention them because Gillian Flynn mentions Velveeta twice in Dark Places—and also in Gone Girl.
Is Gillian Flynn in the pocket of Big Kraft, the maker of the not-quite-cheese product that's a big hit south of the Mason Dixon line? We have no idea. All we know is that this simple recipe of white bread + mustard + "thick smushy chunks of Velveeta" (10.6) that Libby makes for herself in chapter 10 and for Krissi in chapter 22 makes us want our own little square of processed, melt-in-your-mouth heaven.
Okay, yeah, or maybe they stand in for the unnaturalness of Midwest life or for Libby trying to find a substitute for healthy behavior.