After such a whirlwind series of events in Glow, I was super excited to get to Spark and see just how Waverly, Kieran, and Seth are handling things aboard the Empyrean. With Spark, it took awhile before things started getting serious and exciting like how they were in Glow and I was a bit disappointed in that it wasn't as action-packed as Glow, but it was still a decent continuation of the plot and necessary to the overall story. I'd say the best part was the ending, that definitely left me wanting more! 
 Things have definitely taken a turn for the worse between Waverly and Kieran and you see their relationship start to crumble in more ways than one. They have changed so much after the the attack from the New Horizon. Even Seth is showing a more noble and heroic side of him, although after what happened in Glow, I still can't really feel for the boy. Not to say I'm siding with Kieran either because he's slowly becoming more delusional and letting the power get to his head. And Waverly has definitely been affected by what Mathers, the leader of the New Horizon, did to her while she was held captive and along with the tension from all the other kids aboard the Empyrean, you start to see a darker side of her. 
 Whereas Glow was more adventurous and thrilling, Spark deals more with the characters and how each of them are struggling to adapt to their new lives and figure out how to live harmoniously, all the while keeping a lookout for surprise enemy. There's a lot of inner turmoil and self-realizations that happen with each of the main characters, which is understandable and pivotal to the overall plot and progression of the story. It's crazy how serious things get and often times you have to stop and realize that the characters are all still kids dealing with things that even a lot of adults have a difficult time grasping and I think in that way, Ryan's writing and creativity truly shines. 
 Spark is a great sequel to an already thrilling and fast-paced series with a mysterious plot that seems to get deeper and deeper, characters that are being pushed to their limits both physically and emotionally, and a stellar ending that leaves the reader begging for more. I can't wait to see how this series ends and I can't believe I have to wait like another year to do it!