This book was a fun adventure, with some key characters from the first book, and some interesting new ones. One of my favourite parts was Wangchuck and his monks meditating with the children.
The frost beasts weren't as exciting for me as the nazis and Rome, and I really like how Brendan comes to realize he should be with his sisters. The plot twist from the diary of the Wind Witch's mom wasn't necessary, in my view, because there's enough drama between the Walkers and Witch already. Still, it may play into the next book in the series, one never knows.
Looking forward to the next adventure.