Wax is a Lawkeeper in the Roughs. He is probably the most famous and successful of the Lawkeepers out in the Roughs. He is dedicated to his job but gave it all up and moved back to the big city when tragedy struck. In the city he decided to stick with the family business but a mysterious crime happened. Trains were being robbed; whole carts were emptied but no one ever sees the robbers and the train is always undamaged and locked. Wax tries to stay out of it but when robbers started to kidnap people well...
If you haven't read Mistborn before you won't miss out on anything as the book is a standalone.
If you have then...
The Alloy of Law is set in the same world as Mistborn but around 200 years later when automobiles are just coming onto the market and guns are a plenty. I know for a fact that a lot of fantasy readers are immediately put off as this book suddenly changes to a "Steam punk" genre. However, I was never disturbed by the fact that there was technology in the book. I felt that because of the magic system Sanderson uses in this world, technology only helped to enhance it.
The intriguing part is that Mistborns are no longer; only Mistings. However, the frustrating part is that Sanderson doesn't solve this issue in this book so it feels like a season of lost where you've read it, but only asks more questions.
As for the book itself, it is written in the same Sanderson manner. Fast paced, small little twists and characters that you cannot help but like.
Another winner by Sanderson.