There's a map! I don't know about you, I love it when fantasy books provide maps, it shows that the author put effort into world building, and want you to be immersed in this world as much as possible.
With the preface, and the brief glimpse into Talin's past, Marie Lu makes me want more. Then with the incident that happens to her Shield, you know Talin will find a way to prevail, it's just a matter of the journey. At least I hope she does. I'm anticipating receiving my copy so that I can confirm.