What I liked:
The cover- it’s beautiful.
The characters are interesting and realistic. Ruby is a spy, but isn’t applauded when she risks her life and is treated (when not being a master code-breaker/spy extraordinaire) as an ordinary teenage girl. However, her natural talents and intelligence are weaved throughout the story and it’s great having another interesting and intelligent girl as a role model for children.
Ruby’s friends and family are more than just background figures, and their relationships are again realistic.
When the story gets going the spy capers are fun and well written.
The codes throughout the book (and the importance placed on them) are excellent. Cryptography is a fascinating art.
The two things I didn’t like
Ruby’s attitude- she’s quite often downright rude and this is rarely picked up on. She’s excellent when she’s smart and sassy/witty but not when she’s rude for no reason (i.e. when having her cast removed).
The pace: this book took quite a while to get going. Once it did, it was worth the wait, but it took a long time getting there.