The best book in the "franchise" in a long time! 
Rowley's first book was a good starting point to his POV but I'm glad this isn't just another diary-book, that'd be a bit repetitive and too derivative of the Wimpy-books.
Before starting I believed this volume to be a simple little childish fantasy story...which it is but also more. The plot is broken up by diary inserts of Rowley where he explains stuff and Greg's reaction to his writing - instead of disturbing the flow of the story it actually works well and I quite enjoyed it. 
The jokes are pretty great and there are some twists and turns that I lowkey didn't expect - I feel like Kinney would write even more extra if he didn't have to be so kid-friendly... :D