Miss Peregrine's Home for Peculiar Children, I didn't realize it was a series. I think it is a series that could have a lot of potential because you can take the general premise (these kids with odd talents or traits (like having a hole through your midsection as pictured above), and you can make each story it's own - they don't have to build off each other.
That being said, book two, Hollow City, is very much a sequel to the first book. It was a episode 5, The Empire Strikes Back, sort of story to me in that it really is setting up the next book. This is more of a book of self- discovery, a book to teach the reader more about the peculiar people, a book about a journey - literally, and a book not actually about Hollow City - but that's OK.
I am anxious to see what book three brings, and if the author will just start on break off stories, still about peculiars, but stand alone books (like how there's a whole bunch of Hardy Boys books, but you can read any of them, and you can read in any order knowing that it will be about the brother's solving unique crimes. Or maybe like Nancy Drew? Or The Babysitters' Club - never read those, but they may be more your style.) But you get the idea. This is just another fun chapter in the adventures of the peculiar children's lives.
(oh, and a side note - the actual book had quite a waitlist, so I got the book on CD. Kirby Heyborne is the narrator. Kind of funny listening to him read and play all the characters. He did a great job, but funny to me still.)