Serious, Direct, Honest
To Alanna, becoming a knight is Serious Business. Because she's our main viewpoint character, that colors our perception of the story. When Alanna first puts on her page uniform and prepares to meet the other noble boys, she notices that "her hands were shaking" (2.23). Every time someone comes close to finding out about her gender, she gets nervous and reacts very seriously. Makes sense. If you had to lie about who you were in order to have a shot at achieving your dreams, your hands would probably shake, too.
Because Alanna tells it like she sees it, we get a very direct take on life at the palace. She knows that she's signing up for a life of hardship, and she expresses it in phrases like this: "Training was endless. Even once a knight had his shield—or her shield—he still worked out in the yards. To get out of shape was to ask for death at the hands of a stranger on a lonely road" (2.125). Yep, she's not pulling any punches here.
If you'll join us for a brief chuckle, it's pretty ironic that Alanna's tone is so honest, when (1) she's lying about who she is, and (2) she doesn't always know the truth about things. For instance, when she gets her period, she flips out but still describes honestly what's happening to her: "Hunting frantically, she found some bandage and used it to stop the red flow. Her hands shook. Her whole body was icy with fear" (6.1). It's not until later that she learns about menstruation, but her reaction to it is honest and rings true with what we know about her character.
Exhibit B when it comes to honesty is Alanna's reaction to Duke Roger. She dislikes the man intensely, without having any clue why. Alanna's friend Gary (also one for honest speech) asks what's wrong with her, saying: "He was being friendly, and if you were a dog your hackles would've been up" (5.71). And by the end of the book, we still don't have any confirmation that Duke Roger is a bad, bad dude… but because Alanna believes he is, we can't help believe it too.