I have been having a difficult time coming up with a plot summary, I think it may be because I am not entirely sure there was an actual plot. Okay here is a stab. Luce was sent to a boarding school, Sword & Cross. There she met two guys Cam and Daniel and girls Arriane, Gabbe and Penn. They try to navigate around each other and stay alive. Really that is the best I can come up with.
I firmly believe if the author deleted the three primary characters and made a story involving the secondary characters the story would have been much better. I understand she was trying to make it seem as if Cam was mysteriously charismatic whenever he was actually around Luce, but it just made her feel flaky without actually knowing what she was wanting.
Luce said from the beginning that she wasn't going to talk about her past and the events that lead her to the reform school. Then she talks about it with the first two people she met. Then she again told us she wasn't going to talk about it. Luce really stuck to her conviction by discussing it with both of the guys in the story, Cam and Daniel.
One of the things that puzzled me throughout the entire book was the sweaters. Why if they were in the south in September was everyone wearing either a sweater or a hoodie? There was even one character who wore multiple sweaters at the same time. I realize this isn't a pivotal plot point, but I really got stuck on this detail.