This is book three in the Invisible Library series. By this point the characters are all very well developed, and easy to become attached to. We pick up shortly after the events of the last book. Irene and Kai are returning from an assignment only to find things in chaos. They are quickly sent on another assignment as the library finds itself under attack. In what is becoming quite common for Irene (in a good way) things quickly take a bad turn, and she must find a way to save the day. The story keeps you hooked from beginning to end. I am really looking forward to the next installment.