These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Call Forward: If I recall correctly, Perse at one point is described as having a red spot/blob/mark on her forehead. This could very easily put the book into the Dark Tower pantheon, which would make Perse a minion of the Crimson King. Jerome harkens to the beam breakers. The three are, of course, a ka-tet.