Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Ironic
From the beginning, it is clear that Miguel de Cervantes thinks that Don Quixote's efforts to be a knight are foolish. He tells us early on, in fact, that his title character "unluckily stumbled upon the oddest fancy that ever entered into a madman's brain," which is to become a wandering knight (1.1.1.8). But later on, Cervantes says things like: "[I]t seemed no less impossible than unjust, that so valiant a knight should have been destitute of some learned person to record his incomparable exploits" (1.2.1.1). In other words, Cervantes has adopted the language of Don Quixote himself, referring to the character as a "valiant knight" instead of a crazy person.
It's clear that this is mostly tongue-in-cheek on Cervantes's part, since the whole point of his book is to make fun of knight adventure stories in the most ironic and sarcastic of ways. But one of the coolest things about Cervantes is the way he never shows his whole hand. Even when he's making fun of something, he's rarely making fun of it completely. Cervantes wants us to laugh, but he's not here to just give us mindless laughs. There's a lot going on between the lines here.