Never Say "Die": Aomame refers to people dying as "being sent to another world".
Not so Different: Ushikawa realizes that he has a lot in common with Tengo.
Omnibus: Originally published as three separate volumes, the English release combined all into one really big book.
Parrot Exposition: Happens a lot, especially when someone is talking to Fuka-Eri.
Pun-Based Title: The title is a pun on 1984. The number 9 in Japanese is pronounced the same as the English letter Q.
The Red Stapler: Janácek's Sinfonietta became more popular after the release of this book.
Sadistic Choice: Aomame can either kill the leader, causing the Little People to lose any interest in Tengo but result in Sagikake coming after her, or let him live, in which case the Little People will arrange Tengo's death.
She ultimately chooses to kill the leader, but the effects don't get explored in time.
Sealed with a Kiss: The book ends with Tengo and Aomame sleeping together.
Spoiler Title: After 78 chapters of Tengo and Aomame looking for each other, the last chapter of Book 3 is called "Tengo and Aomame".
Strange Girl: Fuka-Eri, the teenage girl whose draft novel Air Chrysalis sets off Tengu's storyline, has a totally flat affect in her speech and seems vaguely autistic, for reasons that become clear over the course of the novel.