I actually finished this a day or two ago, but I got a bit busy. I also felt in this one case that it was a good idea to let myself digest the book a bit before I try to talk about it. I was a little underwhelmed initially, but now that I've thought about it, I did still like the book.
This is the second book in the Sky Chasers trilogy, and in many ways it suffers from what we call "Second Book Syndrome". Because it has to bridge the gap between the exposition of book one and the climax of book three, it's own story is somewhat weak. In the first book, we had members of the Empyrean kidnapped and used by the members of the New Horizon. Glow touched on issues like religion, leadership, reproduction, and human nature. It wasn't a perfect book, but because it raised these issues, it set the bar high for what Spark might have to say philosophically. In reality, though, Spark is mostly about the kids on the Empyrean trying to run the ship and get their parents back. There's a great deal of politics and a lot of arguing. Waverly is torn between supporting Kieran, though she disagrees with his leadership style, and helping Seth, though she finds his dark side distasteful. Then circumstances force Waverly to see her own darker side.
The book creates an effectively anxious tone, with kids trying to run a massive ship that is their only home. I liked that desperate, claustrophobic feeling.
I like that the characters are boldly imperfect. We see Seth's cruelty, but also his humanity. We know that Kieran means well, but we also see his unhealthy arrogance and lust for power. Waverly's experiences on the Empyrean gave her a bit of wisdom, even as they broke her in many ways. The character building is rich and realistic.
I like that the romance (and more importantly, the love triangle), is very much downplayed. We know how the characters feel, but we aren't made to linger on it.
The plot itself is, as mentioned above, really underwhelming. In terms of action, there is some, but it doesn't last long. It's resolved quickly and predictably. In terms of social and political conflict...again, it's there, but there isn't enough tension to any of it.
The character behavior goes way off the rails more than once, and it's hard to read. Even when it's understandable, its infuriating. They make stupid choices, arrogant choices, mean choices, and it's a bit like watching a train wreck.
If you liked the first one: yes, you should read this one. However, if you were not a fan of Glow, I doubt Spark will win you over. It's a decent read, but the plot is a bit of a let down. 3 stars.