I thought this was an entertaining book. Frankie was pretty analytical about some things, and very much a teenage girl in others. One thing I was disappointed in, though, was how the narrator (and the back of the book) really built Frankie up to be a genius. She was certainly smart and definitely had a lot of ideas that were unusual, but it wasn't brilliant when you consider what kinds of things she was studying.
The hardest part of the book to relate to was the boarding school aspect, just because it's something that not very many people have experience with. I would recommend this book particularly to freshmen and sophomores, but older grades would probably enjoy it, also.