Just finished reading this book and wow, Marcus Emerson does it again! The way he blends humor with mystery is perfect for young readers (and even us older fans).
The crossover with Diary of a 6th Grade Ninja was my favorite part - seeing familiar characters in new situations felt like meeting old friends. The illustrations are super detailed too!
I totally agree with other reviewers about potential sequel ideas. An amusement park mystery would be EPIC! Maybe we could even see some characters from Secret Agent series pop up?
Small theory: I think Skullcap might actually be Billy. There's this one scene where... but no spoilers! You'll have to read to find out :)
Seriously though, if you liked Diary of a 6th Grade Ninja, you'll love this. Same great writing style but with fresh new adventures!