Help?

My niece is turning 14 this weekend. I have only just now remembered this. With amazon prime, I can order something this afternoon and it will arrive on (or near enough) her birthday that I won't feel like the deadbeat aunt. She loves to read, so surely a couple books would fit the bill. Yet I am drawing a total blank on what the classic young adult novels are.

For reference, I know she loved the Twilight books, and the Sisterhood of the Traveling Pants. I gave her brother a pile of Neil Gaiman books last year, so I can't do that again. I know that there are YA books I've read that would be perfect for her, and yet I cannot think of any; I've got a total deer-in-the-headlights problem with this oncoming birthday. Suggestions?

ETA: Thanks, everybody! I'm all set now -- purchase made, headlights averted. Phew.