Colloquial, Declarative, Sardonic
Think about the first sentence of the book: "I've been called Bone all my life, but my name's Ruth Anne" (1.1). Kind of a strange way for a person to introduce herself, right? A "Hello" would be nice. But it does get us straight to the point: we know right away who is going to be telling the story—and who the main figure of the novel is going to be, no bones about it. (Sorry, we had to.)
The point is: Bone's statements tend to be pretty blunt, and she uses really straightforward language. She doesn't have long, windy sentences that go on for pages, and she doesn't use words that send your running to a dictionary.
Bone makes lots of simple statements of fact that don't dance around the point: "Reese and I hated the honeymoon" (4.10); "In Daddy Glen's family the women stayed at home" (7.39); "I loved her praise more than the money, loved being good at something, loved hearing Aunt Raylene tell Uncle Beau what a worker I was" (12.42). You see what we're getting at? There's nothing wishy-washy, nothing you could argue with—just facts, plain and simple.
Sometimes Bone will tell us about a situation by being sardonic, which is a good word to have in your back pocket. Basically, it means being funny but also kind of mean; it's a bit like sarcasm and irony. Here's an example: when Bone is comparing Reese's paternal grandmother to Granny Boatwright, Bone compares them like this:
Mrs. Parsons wore blue gingham aprons and faded black dresses with long sleeves she would roll back to her elbows. My granny wore sleeveless print dresses that showed the sides of her loose white breasts and hitched up on her hips. (5.21)
Bone is not just poking fun at her Granny for our amusement; she's also exposing her self-consciousness about how embarrassing and un-granny-like Granny is.
When people are sardonic, they're usually showing why they are unhappy about a situation, but in a kind of funny way. It's kind of like saying "good for you" when you really don't mean it. Bone uses it when she gets into the newspaper and describes herself as "Like a Boatwright all right—it wasn't all my blood" (21.9); she makes this sardonic comment to show her exasperation at getting caught up in Boatwright shenanigans.