Hollow City is the sequel to
Miss Peregrine's Home for Peculiar Children. I highly recommend reading that first book, and then this one. The summary includes spoilers! You have been warned.

The children travel to the mainland, in search of help to turn Miss Peregrine human again. With their loop destroyed, the wights and hollowgast are intent on stopping them, and stealing Miss Peregrine back. The peculiars will find new loops and allies, and learn more than they'd ever want about what the wights are planning.
Although I have failed to give a summary worthy of this book's greatness, you should most definitely read this series. Riggs continues to create literary perfection and provides a plethora of creepy photographs. I thought this book was even more thrilling than the first one as the adventure continues and new secrets are unfolded. The ending leaves you eager for more, and I promise there's going to be a review on book three posted- as soon as it comes out.
I'd rate this book 10/10
~Mushu