This is a great prequel to Cinder! It totally explains things about Cinder, her new family and how she became a cyborg. I love that Garan treated Cinder no different than his daughters Pearl and Peony. I don't like how Adri looked at or talked about Cinder. Peony was absolutely sweet just like her father. I love that even at young age, Cinder is very valuable in fixing mechanical things. The ending was so sad, when he caught the plague.
I highly suggest that if you plan to read Cinder and want some world building and character development...READ THIS PREQUEL!