Heyo! I saw that you voted for Blood On Our Hands. I'm just here to say that it's the second book (yes, I made a series XD). The previous book, Before The Storm, explains more about... Well, everything. It's not necessarily needed to understand Blood On Our Hands, so that is up to you!
Also, I'm sorry for all the mistakes and typos and everything. Still editing (even though it might take me a year to finish XD)