Chain Reaction by Simone Elkeles

Luis Fuentes has always been sheltered from the gang violence that nearly destroyed his brothers’ lives. But that didn’t stop him from taking risks—whether he’s scaling a mountain in the Rockies or dreaming of a future as an astronaut, Luis can’t stop looking for the next thrill.

Nikki Cruz lives her life by three rules—boys lie to get their way, don’t trust a boy who says “I love you,” and never date a boy from the south side of Fairfield. Her parents may be from Mexico, but as a doctor’s daughter, she has more in common with her north-side neighbors than the Latino Blood at her school. Then she meets Luis at Alex’s wedding, and suddenly, she’s tempted to break all her rules.
Getting Nikki to take a chance on a southsider is Luis’s biggest challenge, until he finds himself targeted by Chuy Soto, the new head of the Latino Blood. When Chuy reveals a disturbing secret about Luis’s family, the youngest Fuentes finds himself questioning everything he’s ever believed to be true. Will his feelings for Nikki be enough to stop Luis from entering a dark and violent world and permanently living on the edge?

If you're a fan of the first two books in the Perfect Chemistry trilogy, Chain Reaction will not disappoint! I devoured this book and enjoyed every second of it. I've been anticipating this book since Rules of Attraction's release, curious as to how Elkeles was going to tell the youngest Fuentes brother's story.
Oh, Luis, you were supposed to be the good one! In the first two books, Luis is portrayed by older brothers Alex and Carlos as the good brother. The straight A student. They tried to shelter him from gang activity. In this book we got to really see Luis, the thrill seeking, adrenaline junkie side that he tries to keep hidden from everyone else. I loved Luis! I loved that despite his bad boy streak, he's still smart and wants to be an astronaut. While sometimes I didn't like what he was doing, I always understood why he was doing it. Though sorry, Alex is still my favorite Fuentes brother.
Nikki is a great female lead as well. She had that all guys are out to get me mentality, which would annoy me in most cases but I totally understood, considering her first relationship ended with a bad breakup and an ectopic pregnancy. She's the only Mexican out of the three perfect chemistry girls (though she doesn't speak spanish,) and is definitely the most stubborn of the three. She judged Luis too quickly, but she just wanted to protect her heart. And I can't really blame the girl for that.
Luis and Nikki's connection was intense--but their relationship got to be somewhat of a mess. When they finally got together, things got hot and passionate, despite Luis's lies and deception about Latino Blood. I loved how the relationship was about more than the physical connection. In fact, some of my favorite scenes were some of the low key ones. Like when Nikki takes Luis to the animal shelter, or when he's helping her do her math homework. When things were working, they were so cute together.
One of my favorite parts about this book was keeping up with Alex and Carlos lives. That despite the book's focus on Luis, we still got a good sense of what was going on with the other Fuentes brothers. At the beginning of the book we got to see Alex and Brittany's wedding! That made me so happy. And I literally laughed out loud at some of the things Carlos says. The family dynamic set up here is incredible.
The thing about these books that always gets me, that as over the top as some of the gang stuff seems to me, this is a real portrayal. These things do happen. It's horrifying, all of it. Being jumped in, being jumped out, the threats, the tests of loyalty that can ultimately ruin your life. I can't believe that some of this stuff really goes down.
I'm so sad that this series has come to an end. Finishing this makes me want to go back and reread Perfect Chemistry and Rules of Attraction right now! I loved these edgy books and I can't wait to see what Simone Elkeles has in store for us!