This forth instalment is so rich and had a wider plot. Saving one from prisoner, one from an awful master, one from terrifying devil, killing two biggest Boss. As Emily May ever said, this series isn't fantastic read, and you have to be really committed to it since it's a very long story, more than 2000 pages from the current five books and two novellas. But, I've sucks into this world already and it's hard to pull out but keep reading and devouring it 'till the end.