To add to my previous list of GenX authors/books, I thus nominate Mary Gaitskill, who while in terms of her age may not be considered a GenXer, her fiction certainly fits.
Gaitskill is the author of two short story collections and two novels :
Her stories often revolve around a kind of yout culture, especially young people in state of stuckness, between their youth and impending adulthood, which for me places her firmly in the X. Lit realm. But of course, as with many authors/books that I’d nominate for inclusion in the X Lit. worlds, her work definitely reaches beyond such a limiting hermeneutic (I think I used that word aptly, but feel free to take me to task on it).