It was okay. It wasn't a bad book (but it also wasn't the best espionage/coding/mystery book I've read). I would have really loved it, had I read it, say, two years ago. The cover says it's for ages 10-14, and i'm currently 14 and I feel like I was a tiny bit too old to enjoy it. It was really fun to solve the codes alongside Christopher Rowe. Fun Fact: I accidentally borrowed the 3rd book instead of the 1st book, so now I'm reading the 2nd book then onto the 1st. That wasn't funny :)