The Queen's Army is a very short (18 page) story that is 1.5 in the Lunar Chronicles series. If you read Cinder, you will remember them mentioning The Queen's Army in passing, but I anticipate it will have a much larger presence in Scarlet. This book shows how the members of the army are selected, physically altered, and trained.
Z is selected at the age of 12 and is taken from his family to begin training. He is subjected to ruthless physical and mental challenges/abuse as part of the development process. As he grows and matures he becomes one of the strongest members of his "pack"....yes, think werewolves. One day, the queen arrives and wants to see two members from each pack demonstrate their skills. Will Z be able to stand up to the test?
Overall this was a great introduction and behind the scenes look at what the Queen has in store for Earth. We have already witnessed her mental manipulation and this army will add the physical force she likely needs to take over Earth. I really hope Cinder, Emperor Kai, and the rest of the characters we met in Cinder are able to conquer this ruthless dictator.
I strongly advise reading this short story if you plan on continuing the Lunar Chronicles series. There is a lot of background information that likely isn't presented in Scarlet. It is a free download and should take less than 30 minutes of your time to complete. The knowledge gained is well worth the investment of your time.