Make no mistake, this book does not repeat the disaster that was book #2, but instead achieves a lacklusterness in its own right. While not a bad book, it's also not a good book. The plot generally holds together, but does depend on the stupidity of the villains. If stupid villains annoy you, then you will be well and assuredly annoyed. The story generally works, but with so many characters running about, caring about any of them becomes something of a trick.
If the book had been written by some proper comedy writers, it could have worked. Unfortunately, adequately written comedy is experientially lame. Yet, I can't blame them for skewing this direction, because that was the center of the story and really was where it needed to go.
In many places, the story felt rather padded, walking through the plot with little engagement, while in other places, the story skips over interesting parts of the plot, summarizing as it goes. This is pretty much in line with the other books in this series.
Don't put this book down in the middle because you likely won't pick it up again.