Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Mystifying and Mesmerizing
In Tortilla Flat, Steinbeck uses words that reveal his intention to elevate his characters to the point of being almost mystical beings. They're really ordinary folks, sure, but the narrator thinks there's more to them that that:
That not too perfect Pilon, who plotted and fought, who drank and cursed, trudged slowly on; but a wistful and shining Pilon went up to the sea gulls where they bathed on sensitive wings in the evening. That Pilon was beautiful, and his thoughts were unstained with selfishness and lust. (2.19)
Words like "unstained" and "lust" give this a sort of religious, mystical tone, and the long sentences and insistence on Pilon's beauty and perfection are almost hypnotizing. Steinbeck elevates these ordinary sinners to the level of angels. In a way, that's one of this novel's primary goals: it wants to show us the beauty hidden in ordinary people and in everyday humdrum existence.