This is the second book in the Looking Glass Wars (I think it is supposed to be a trilogy). I liked the first one very much, this one was good too, but I felt it was a bit busy. Like many "middle children" in a trilogy I felt this one was so busy advancing the plot for the big finish that there wasn't much substance to this one. The characters seemed a bit thin - but really, only in comparison to the first book.
Still, very good.