This book is the start of a companion series for the Mistborn world, it takes place 300ish years after the original trilogy and is a flintlock fantasy. I wouldn't recommend picking up this series if you haven't read the original because while it can stand alone, Sanderson builds the world much better in the first trilogy. Also there are some spoilers for the first trilogy in it.
This series follows Waxillium Ladrian, a nobleman who has been living in the roughs acting as a lawman. Following the death of his uncle he is called back to head the house, but doesn't leave until his wife is killed investigating a crime. He then finds himself trying to secure his family legacy by marrying a noblewoman in the city, and investigating a series of crimes happening in the city.
I really didn't like this book nearly as much as the Mistborn trilogy. At first I though that flintlock fantasy may just not be my thing, but the more I dug into my thoughts on it I realized there were a lot of writing/story things that just didn't work for me. Right off the bat we have Wax's wife getting fridged, which is one of my most hated tropes. Then through the rest of the book the women are just not written very well in my opinion. Which was very disappointing.
Also this book was a lot shorter which didn't lead to a more concise story but rather a story that felt like it was missing chunks. Things weren't explained very well, and the characters (with one exception) felt really flat to me.
The one character that I really enjoyed was Wayne who plays the comic relief and deputy to Wax. He was funny and just overall more interesting to me.
I decided to keep reading in the series because this wasn't a bad book it just wasn't great, and I do generally enjoy Sanderson. Also this was the first flintlock fantasy that I'd read so I didn't want to just bail on the whole thing without giving it a bit more of a try.