The fourth book in this series, and by far the best. It was so good having all the characters from the previous books together, but I really hope there is more to come from this series. I'd love to see more of Levi growing up. 
I loved absolutely everything about this one, and while it was the longest of the four books, it took me the least amount of time to read as I just couldn't stop reading. 
Highly recommend this whole series.