This is such a wonderful extension of the Ember in the Ashes universe! I'm not surprised that I loved this, though I will say that I probably wouldn't recommend reading it before reading the Ember quartet. Tahir does a good job summarizing events from the original series, but there are spoilers included. 

Sabaa Tahir does such a great job writing characters and emotions in this world she has created. You'll be hooked by them from the beginning, it wouldn't be an Ember book if there wasn't some emotional turmoil. I am definitely excited to see where the series goes next!