4.5 stars! This was my favorite one by far!! I loved it because: 
 1. While I enjoyed the boy antics and how they're compared to spy antics, I felt this one kicked it up a notch because there's a lot of mystery and legit spy antics for reasons. Like not boy reasons. 
 2. Cammie didn't spend the whole book doing what she was told not to, like the last book. She still did some *sigh* but nowhere near as bad. 
 3. We learned stuff! We finally got some information about some of the mysterious characters in this book. And we got surprising information about characters we thought we knew. 
 4. The action was edge-of-my-seat, hold-my-breath, scream-at-the-audiobook type action. 
 5. It ended with a major cliffhanger! On to book 5 I go!!