A noteworthy feature of this book is that Zeb, one of the villains, comes across as rather a decent chap at his work on the railway tracks. He fairly gladly shows the boys the points, and talks to them about the goods trains. Still, not to turn too far from the stereotype, "mean-looking with shifty eyes" is his description in the book.
As the fourth book in the series, this story is quite short and sassy. The book has a lot in similarity to the `Famous Five' books especially because Susie starts Famous Five. It paves the way for a series of similar but more complicated stories to come. I would rate this book: 7/10.