Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Matter-Of-Fact, "Objective" (In The "Plain And Detached" Sense)
The Stranger is written in a forthright, matter-of-fact, and unadorned style. There's little color to the novel... even though it has some poetic qualities. Without the occasional irony or sarcasm, however, a reader might even mistake its simplicity for boringness. The novel is peppered with bone-dry observances like this:
Then he offered to bring me a cup of coffee with milk. I like milk in my coffee, so I said yes, and he came back a few minutes later with a tray. I drank the coffee. Then I felt like having a smoke. But I hesitated, because I didn't know if I could do it with Maman right there. I thought about it; it didn't matter. I offered the caretaker a cigarette and we smoked. (1.1.13)
It kind of sounds like he's about to launch into saying, "I had this dream. I was in my house, but it wasn't my house, you know? Then there was a cat, but like it was a cat with a dog's face." It's half-mesmerizing and half yawn-inducing.
Don't be fooled. Because the novel is told by Meursault (half-man, half-lizard/robot), the tone is necessarily defined by his voice. What seems "boring" is really an incisive insight into the main character. We are forced to see the world the way Meursault does; as a series of monotonous, timed, unexciting events. This makes the tone of the last two pages (when Meursault lets loose, existentially) all the more exciting.