Pride and Prejudice and Zombies is, as you might imagine, a bit gimmicky. It's the kind of book that looks great on the shelf and will never fail to elicit some titters. It's a book that makes a great novelty gift, but that I can't see too many people buying for themselves. 
 Because it really is a gimmick. Grahame-Smith adds fairly little to Austen's original work. What does get added is a bit clunky. The writing doesn't match Austen's style very well, zombies notwithstanding. 
 The strength of Grahame-Smith's version is in the world building - how a different era might respond to a zombie crisis, how such a hierarchical society might encoroporate zombie fighting training as another measure of class (the wealthiest are trained in Japan, while the lower echelons of wealth train in China). Unfortunately, Grahame-Smith is so bound by Austen's writing that he doesn't really go far enough with it. 
 I enjoyed the story, but mostly as an opportunity to revisit one of my favourite Austen novels. What Grahame-Smith adds is a little weak, but still fun. There's a joy in seeing Lizzie Bennett slaughtering zombies!