Steampunk plus zombies plus airship pirates. That's Boneshaker (Sci Fi Essential Books) by Cherie Priest in a nutshell. In nineteenth century Seattle, mad scientist Leviticus Blue invents a massive mining vehicle called the "Boneshaker." On its test drive the Boneshaker tears its way through the city (and in a suspicious manner through the banking district) and in the process releases a subterranean pocket of gas which turns people into zombies. A little over ten years later the infected portion of the city is walled off and Blue's widow, the young Briar Wilkes, is living with the stigma of being related to the late Blue, who reputed died during the test drive. Wilke's son, Ezekiel decides to enter the walled-off portion of the city to prove his father's innocence, and Briar goes after him to rescue him from zombies, survivors living in the walled-in portion of the city, and the aforementioned airship pirates.
Boneshaker is a chunky book full of detail and interesting characters, but at times the plot seems to meander about aimlessly, mostly to accommodate the introduction of one curious steampunk fixture after another. There's not much of a antagonist, just the shadowy "Dr. Minnericht" who may or may not be Leviticus Blue. After dragging along for three quarters of the book, the plot suddenly hits the gas at the end, almost to the point of feeling rushed.
If you're a steampunk fan, the book is a must read, especially if you like a good, solid female protagonist. If you're a zombie fan, this is probably a pass, since the "rotters" are very much on the periphery of the story. The "Blight," the name for the zombie-producing gas, is more of a peril than the zombie themselves. I found myself initially excited about the book, then sort of losing interest about halfway through, then barreling through the back half in one sitting.