I liked this book. If it was possible, I'd give it a 3.5 star rating, because I did enjoy it. I have some mixed feelings though. Spoilers passed this point!
On the one hand, I'm super in love with steampunk, steampunk, and more steampunk, so I loved all the descriptions of the gadgetry and the world building was fantastic. Zombies! Gas masks! Triple-barreled guns, and guns called "The Daisy Dozer." Airships! My beloved goggles! All elements brought together to form a world that I can get immersed in. The set-up of the story is fantastic, as the author describes a harsh world struggling to recover from the aftermath of a terrible disaster. We have an illicit drug trade, blighted rains, and too few natural resources to go around. The country is torn apart by The Civil War, so there is little hope of outside intervention. This was all very carefully crafted, and I tore through the first third of the book as a result.
Then the main character is forced to go into the ruins of Seattle in search of her wayward son, and the author loses focus a bit. The gadgets are awesome, the underground society is fun, but there are too many elements that fall flat or aren't resolved at all. The antagonists' motivations are unrealistic, and we don't get a sense of how many people actually live in the city underground other than the small group we're introduced to. So all of the unrest and revolutionary talk doesn't have the teeth it could have, and the uprising at the end isn't as exciting. There were a few useless side-trips that caused the plot to meander, and I just feel this time could have been better spent paying attention to elements that were already introduced. And as for the conclusion...I am just not a fan of the Sherlock Holmes style resolution in which the main character reveals everything in a few pages of exposition. There were too many things left dangling. I understand that there are further books set in this universe, but there were issues particular to this story that could have been addressed.
Despite my issues, I did enjoy Boneshaker, as I think many steampunk devotees will. I'm not as sure about the reaction from people who aren't great fans of the genre though.