They manage to find a loop full of peculiar animals, who help point them in the direction of London and Miss Wren, who will hopefully be able to save Miss Peregrine (who is stuck as a bird). They get captured by Wights, fight their way free (thanks to Horace and his bees). Make it to London and another loop. Find a pigeon to guide them to Miss Wren. Find yet another loop where Miss Wren is hiding. All while running from wights and hollows. And encountering more peculiars along the way.
Honestly, by about 30% of the way through the book (it's a Kindle ebook that I was reading) I was bored. But I persevered through to the end. There's a crazy awesome twist at the end.
(the bird they've been carrying around ISN'T Miss Peregrine!)But it isn't enough to keep me interested or make me want to read more. So at the very least I'm going to go and read something else. Maybe I'll come back to this series and finish it in the future. But then again, maybe I won't.
I should also add that the pictures, which made the first book more interesting, really detracted from Hollow City. Things that happened felt contrived to fit a picture. And I felt like the book relied on the pictures too much to show you what things were like rather than leaving them to your imagination.