The Bastables are one of the prototypes for kids who innocently get into trouble. Their hearts may be in the right place but they have serious issues with bad judgment and poor impulse control.
In the Wouldbegoods, they set out to become better people during a summer holiday in the countryside. A holiday that they were required to go on after wrecking their uncle's yard and taxidermy collection. Needless to say, chaos follows every good deed they tried to do and every game they try to play.
I pretty much have to compare it to the first book, the Story of the Treasure Seekers. On the one hand, I found the second book a more enjoyable and fun read. And on the other hand, I found the first book to be deeper and more meaningful.
You see, the poor judgement of the Bastables makes you seriously wonder if there is something wrong with these kids. And, it becomes rapidly obvious in the first book that there is. Underneath their jolly play, they are clearly traumatized by the death of their mother and by their father losing everything when his partner embezzled the company into the ground.
Their lives are much improved by the second book, which means that we are not reading about a group of kids who are clinging together in order to keep it together. Which is definitely more upbeat but not nearly as moving.
One thing that I have to give these books is that the kids don't get away with any of their accidental hijinks. There are definite consequences to their actions. One of the most striking scenes in the book is the younger daughter practically having a breakdown after discovering that a good deed overturned a barge and dump out a load of coal. The kids are well aware of how many scrapes they get into, even though they can't seem to learn from them.
The book does get kind of formulaic. Each chapter, we read about how the Bastables have some kind of poorly thought idea and how it will inevitably blow up on them. It's not one of Nesbit's strongest works, particularly compared to the first book.
Still, the Wouldbegoods is an interesting, if sometimes dated (and even racist) look at the beginnings of modern children's literature.