I recently finished a very fun YA book called The Grimm Legacy by Polly Shulman. It was a fun fast read that I immediately handed off to my daughter when she was heading up to reading time before bed. She finished it that night (I think she reads faster than I do) and handed it off to her sister the next morning. Curly is now about half way done and her Grandma has claimed that she gets it next.
It's about a teenager who doesn't fit in well at school or home and so when one of her teachers recommends her for a job she jumps at the chance. It happens to be a job at a library in New York that lends items instead of books. After she's there for a while (and in the midst of confusion and possible mysteries) she discovers that there are a couple of special collections in the building. The story is fun but not too complicated, and definitely held my interest. I think it's kindof the flavor I hoped the Grimm television show would be before I watched it and discovered what it really was.
(I also read Prisoners in the Palace - a YA book about Princess Victoria, and Midnight in Austenland - an adult book about a place where people can immerse themselves in Jane Austen for a couple of weeks vacation. Both were fun, neither grabbed me as much as Grimm legacy...)