Anyone can be a spy. Anyone can be trying to smuggle secret messages into your world. Anyone can be out to get you. So get your tinfoil hat and prepare yourself.
I don't give books star ratings; I give them bite ratings. This is a bite. A book can get up to five of these evil-looking chompers, including half bites.
You can attribute your own wording to the ratings. Five's the best, three's decent, one and under isn't worth the gas to go to the library. I'll leave it to you to fill in the blanks.