One thing for sure, there is a lot of keys in this series!! That being said, I find the concept really good and the originality of it is just mind blowing, but the problem I have with it, because I have one, is the fact that everything evolve so slowly. We're ending the third volume here and nothing really new happen, won't enumerate it because don't want to spoiled anything, but it's more or less the same stuff that happen in the first volume. The illustrations are very beautiful, the action is good, but there is not enough, a bit to slow and the overall feeling is yeah another key!! New magic stuff a new door can do, and then we go back and start everything again. I just hope for a major break point here so it will feel like the story is really evolving, because I don't feel it here!