Ms. Peregrine's Peculiar Children #2: Hollow City by Ransom Riggs

Jacob and the other peculiars narrowly escape from the wights and hollows, but Ms. Peregrine's home has been destroyed. She's a ymbryne, kind of the guardian of the peculiars, but she's now stuck in her bird form, possibly forever. The children discover a loop and travel back in time where they meet many other peculiars. It seems someone is trying to capture all of ymbrynes in the world, but the peculiars don't know why. The children must travel to 1940's London to find Ms. Wren, the only free ymbryne left who might be able to save Ms. Peregrine. The journey will be dangerous with WW II bombs dropping and wights and hollows hunting them down. The peculiars are doomed if they can't save Ms. Peregrine and the other ymbryne.

Peculiars are gifted (cursed?) with special abilities or powers. One of the main characters is invisible, one can create heat and fire, and another can control bees. The author creates a conflict by having Ms. Peregrine stuck in bird form. She's still able to communicate with the peculiars in her own bird-like way, but her time is running out. Each character performs a role with the group in order to survive. Emma is the brains, Jacob is the hollow fighter, and Bronwyn is the muscle. A unique addition to the book is the collection of unusual photographs. The plot describes a girl with a hole in her stomach and a foldable man, but it also displays old-time photographs of them. Some of the pictures are a little freaky. You should read the first book in the series before reading this one, but it's not absolutely necessary in order to enjoy it.