Yeah, it's from
Blood Meridian 
Blood Meridian seems like the kind of book someone would either really like (if they can stomach it) or really hate.
It's definitely not something your average school girl would read (and certainly not Kit), but I figured it'd be fun to mention it in the comic. It's sort of a combination shout-out. It's a shout-out to Cormac McCarthy and Blood Meridian, and it's also a shout-out to Jeff Smith, who frequently referenced Moby Dick in his comic "Bone" (which was also a kind of fantasy story).
Moby Dick and Blood Meridian are sometimes compared, for instance:
" In the entire range of American literature, only Moby-Dick bears comparison to Blood Meridian. Both are epic in scope, cosmically resonant, obsessed with open space and with language, exploring vast uncharted distances with a fanatically patient minuteness. Both manifest a sublime visionary power that is matched only by still more ferocious irony. Both savagely explode the American dream of manifest destiny, of racial domination and endless imperial expansion. But if anything, McCarthy writes with a yet more terrible clarity than does Melville.
—Steven Shaviro, "A Reading of Blood Meridian""
(that's from the Wiki article on Blood Meridian)
(McCarthy writing "terrible" clarity is...very accurate. Blood Meridian is just a
heavy book.)