>>149675856
It's worth noting that the books are also their own thing entirely, with a more zany and chaotic story; every book ends on a cliffhanger that raises the stakes until eventually the guys who were trying to get a cat out of a tree are fighting for the fate of all existence.
You could charitably say the first movie adapts books 1-4, but 2 is a lot more it's own thing, mostly built around the rocket heist that happens in book 5 and bringing the girls in from book 8.