Boneshaker by Cherie Priest
Welcome to a crazy alternate-historical steampunk world, starring a plucky and determined mother/son pair who must use all their wits to escape from a Seattle that has been taken over by zombies. Priest does some great world-building that literally immerses the reader (bring your extra filters, kids, the air isn't fit to breathe) and goes most authors one better by leaving much of the zombie horror offscreen. You'll focus more on intently listening for a rotter's shuffle than you will on the occasional gore, making the story trip along much more like J-horror than a Saw-fest. My YALSA blogging buddy Ken Petrilli has declared it full of crossover teen appeal.