Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Moralizing
In "Narrator Point of View" we drew your never-wavering attention to the few moments in the story in which the narrator gives us a piece of his mind. What these moments tell us is that he views Le Morte D'Arthur as having some important lessons for his audience and, to be honest, his tone is a bit teachy and preachy, to boot. In fact, you might even call it moralizing.
What do we mean by that? Well, a moralizing tone is one that somehow judges events or characters. One way or another, it tells us readers what to think about what's going down. But Le Morte D'Arthur doesn't do this by giving us that judgment outright. Instead, we know just what we're supposed to think based on the adjectives it uses to describe people and events. Clever, huh?
For example, consider the book's take on Mordred and Aggravayne, who bring the accusation of treason against Launcelot and Gwenyvere. The two are described as "unhappy," or somehow ill-favored knights who bring about a "great angur and unhap that stynted nat tylle the floure of chyvalry of [alle] the worlde was destroyed and slayne" (646.9-10). Just in case you couldn't tell by their actions, our narrator makes sure that we see this pair as evil, and the events they bring about as evil, too. After all, they destroy chivalry. Does it get any worse than that?
Plus, when Arthur lands on the shores of England after Mordred has taken it over, we can almost hear the moral indignation in the narrator's voice as he tells how Mordred was "redy awaytyng uppon his londynge – to lette hys owne fadir to londe uppon the londe that he was Kynge over" (681.1-2), and how the ensuing battle caused the death of "noble men of armys; and there was muche slaughtir of jantyll knyghtes" (681.3-4). Friends, this is not neutral language. It's pretty darn clear that Mordred is in the wrong here and Arthur in the right.
By contrast, many of Arthur's knights are described as "mervelous" and "noble" most of the time (113.3, 8). What's awesome about this tone is that for most of the book, we know exactly where we stand. We know whose side we're supposed to be on, and who has acted honorably and nobly (and who has not). The challenge, then, is to decide whether or not we agree with the narrator's morals in the first place. But that's a whole other enchilada.