I do suggest you read Perfect Chemistry and Rules of Attraction before reading this novel so that you know the Fuentes brother's back story.
This novel follows Luis in his senior year of high school as he deals with moving back to Chicago; his attraction to Nikki, who doesn't like him; and the Latino Blood (LB) gang that wants him to become a member.
Elkeles alternates chapters between Luis and Nikki so I knew they were going to end up together just like his older brothers end up with their future wives, but I was clueless along with Luis on his connection to the LB gang, except that his older brothers used to be gang members too. I vaguely remember the secret Luis finds out from the earlier novels, but I'm not sure if I am imagining it or not.
After reading other novels these past couple of weeks in which the teachers at the school turn a blind eye to the bullying that goes on in the classroom, I can say that I enjoyed the interaction Luis has with his chemistry teacher, Mrs. Peterson, who shows tough love in the classroom with the students but also shows she cares about them too.