This is an interesting description of a little moment in time, when Luna is captured by the Death Eaters. It is written in the first person, from Luna's point of view. The short sentence structure evokes her unique thought processes. She jumps, in her mind, from topic to topic, and thoughts of the imaginary creatures invented by her father intrude on her attempts to understand what is going on around her.
The first conversational section, between Neville and Luna, seems unsubstantial to me. I'm not sure what it contributes to the main theme of the story. The collection of short paragraphs that follow are a good description of the changes and deterioration of the environment in the school and in society in general as Voldemort rises in power. Then the last of these short paragraphs, where Lune speaks of the Crumple-Horned Snorkack, reminds us again that her grasp of the situation (and therefore her reaction to it) is still distorted by her belief in her father's "crazy theories".
In the end, she is too distracted to protect herself, to Ginny's great frustration, when the Death Eaters seize her and take her away. She asks, "How do you Disapparate?" but I do seem to remember that somewhere in the books Luna says that her father taught her to Apparate when she was younger than the usual age for Hogwarts students to learn the skill. (Maybe I disremember.)
Writing Luna must be a challenge. (I have never tried it.) It would be a mistake to stereotype her as a ridiculous figure. She was not a stupid or crazy person, despite her adherence to her father's beliefs. She was a successful Hogwarts student, but with a unique outlook on life and a remarkably even temperament. The author has captured her personality well.
I LOVED Luna's thoughts about the nargles! (and wrackspurts, etc.) Although there were a couple of typos scattered through the story, and you should expand some parts, I generally liked it.
Short but tells the story. Very believable Luna.