Best of the series so far.
Some parts a bit overdone, and completely unneeded (such as the time when the students went to visit the Shackamaxon. The chapter reaching there was a long read, and in the end we learned nothing of it, because next thing they all were back at the school.
I still hope that the author of this will rethink the fact that all grades of the school have lessons together. It would be rather intelligent first years or daft seventh years students if they all take classes together.
It was a good read however, and it could almost be a book written by J. K. Rowling herself.