The Forest of Hands and Teeth, by Carrie Ryan

In Mary's village, no one has ever questioned the Sisterhood's claim that nothing lies beyond the fence except for zombie-like "unconsecrateds." But Mary's mother has told her stories about life before the Return (i.e., before the unconsecrateds took over the world).  She's told Mary about the "ocean," a place with water as far as the eye can see.  And Mary wants to see this place.

While Mary struggles with whether to obey and stay within the safety of her town's walls, events overshadow her doubts, beginning with the arrival of a stranger to the town.  With the presence of an outsider, Mary is certain that there really must be something in the forest and beyond.  And when a catastrophe befalls the town, Mary and a small group of friends are forced to flee and find out.

In all, it's a post-apocalyptic zombie adventure with a romantic triangle thrown in (Twilight meets I Am Legend).  It's not high literature, the plotting is messy, and the writing a bit too dense, but the pages turn quickly.  Don't get too attached to the romantic thread or any of Mary's struggles with coming-of-age, because no character development is really as important as moving this story along at a brisk pace.