This really is a strange book. It's a suspense story through and through, that suddenly gets comedic in the second half. In the first half, Malcolm is trying to convince Amy and everyone else he can talk to that he did indeed witness a kidnapping, and meeting with little success, as clue after clue turns out to be rather flimsy. Once they're at the kidnappers' house, and having gotten captured themselves, Amy and Malcolm have to try to orchestrate an escape for themselves and Jennifer and Clifford.
What's strange is how the book suddenly becomes so silly once they reach the kidnappers' house. Cartoonish bickering between Jennifer and Malcolm, Amy and Jennifer, and the kidnappers amongst each other doesn't quite blunt the suspenseful situation so much as it adds a lot of comedy to it. Yes, one of the kidnappers is pointing his finger through his pocket and pretending he has a gun. Yes, Jennifer and Malcolm trade insults at each other, and Jennifer just won't shut up. And yes, the kidnappers have some sort of complex involving their childhoods that causes them to bicker and argue a lot, being brothers who don't get along.
But the events of the story largely play out the same way they would in any suspenseful kidnapping story. Amy tries to escape out a window by climbing down a tree, falls off a branch, and twists her ankle. The kidnappers tie up Clifford and the kids and leave them that way overnight. They threaten Jennifer out of anger and scare and upset her. None of these situations are funny, and none of them are intended to be funny.
What makes the mixture of humor and suspense mostly work, in my opinion, is that the two are largely separated. The suspense is in the plot. The humor is mostly in the character interactions, plus a few mildly comedic situations that occur. The core plot itself can pretty much work even without the humor. But Jennifer's super-brattiness, Malcolm's inability to put up with her, Clifford's Cloud Cuckoolander
-esque ramblings, and the kidnappers' bickering add personality to the story. What would have been an average, albeit suspenseful kidnapping tale becomes instead a fun, comic suspense story.
Ultimately, it's a pretty fun read, both for the plot itself and for the humor that colors it.