Hollow City: the Second Novel of Miss Peregrine's Peculiar Children by Ransom Riggs

Back in 2011, I read the first book in this series and said that it wouldn't have been anything special without the photographs.  I think the author got it right this time around.  The plot surrounding the photographs makes sense, and you don't have to keep reading just to find out more about the photos. 

Miss Peregrine has been turned into her birdself and the children must travel around to find someone who can help her. They are being hunted by Hollows and other people who want to hurt them though.  All the children's powers are needed to save things, and, even at the end, it's clear that they will still need them in the next book.  Things are not resolved, but Jacob has discovered that he is needed in the peculiar world to help his friends. Looking forward to Book #3!