Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Wry, Playful
Azalea is our main viewpoint character, and even though we largely see things through her eyes, her perspective is not the same as our overall third-person narrator, who basically sets the tone for the book. And that tone, dear readers, manages to be amusing even when Azalea is not amused.
Even though Azalea's not the practical joker that her sister Bramble is, her actions can still convey a wry sense of humor (for us, if not her). For instance, when she's trying to get rid of one suitor, Lord Howley, so that she can look for the missing magic tea set, she tells him to go describe his political plans to her father, saying, "Oh, yes. He loves it when people tell him how to run the country" (17.49). This gives us, the readers, a chuckle, since we know that the King likely doesn't take advice well.
When it comes to unexpected situations, the tone of the book is often light-hearted and playful. Like when Azalea falls into the stream in the royal gardens and Mr. Bradford fishes her out, her inner dialogue is as follows:
He's talking to you! her mind yelled. He's talking to you! Say something clever! Say something clever! Azalea said, "Mffloscoflphus?" (17.58-59)
She's embarrassed at not being terribly articulate around the guy she's starting to develop a crush on, but we get to be amused at this funny turn of events. The fact that the tone is accessible and down-to-earth lets us enjoy the playful and wry humor that abounds in Azalea's life, even though she's often embarrassed by this stuff (and especially by the antics of her sisters).