Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Cold, Rugged, Emotionally Distant
The tone of All The Pretty Horses is a lot like our boy John Grady Cole: not very flowery, emotional, or friendly, and not prone to digressions or speechifying. You won't see any question marks or exclamation points in the narration itself. Since the setting itself is pretty barren (see "Setting"), much of the descriptive language of the novel creates a cold, vacant feeling.
Take the opening description of the Texas ranch where John Grady Cole grew up:
"In the distance a calf bawled. […] Inside the house there was no sound save the ticking of the mantel clock in the front room." (2)
The short sentences, silence, and lack of nearby life here is fairly common in the novel, and is also described at certain points on their journey through Mexico: the descriptive language will sometimes linger over features of terrain, but life, sound, and movement barely register.