Quick-take: Though it is not as strong, if you liked book 1, you should like book 2.
I appreciate Heather giving her characters a mild case of hibernation amnesia as an excuse to remind me of some key plot points --even so far as to have Cassie, the main character, reintroduce herself as she jogs her own memory. Very clever.
While book 1 is Hunger Games meets Space Camp, book 2 is quite the sci-fi action/adventure. The stakes are much higher, and apparently so is the language. After reading the first f-bomb, I thought maybe something got missed in editing. Then a short while later it dropped another one. Then I knew Heather was not fucking around, and shit is about to go down.
It makes sense. Cassie and crew is no longer in high school, and young adults sometimes have foul language. It still caught me off guard. Note, this is not Scarface. It is just sprinkled here and there.
This book was an entertaining ride, but I have a few complaints.
Cassie is a bit whiny. When she is not busy emoting the extremes of every detail, she is second-guessing every major and minor choice she has made. Life as Cassie must be exhausting. She badly needs a beer to mellow out a bit. My problems with her from the first book did get improved. She no longer just reacts to others and can develop her own strategies.
Luca does not seem consistent. Luca is simultaneously aloof, caring, perceptive, awkward, experienced, inexperienced, and a tech prodigy. I just can't wrap my head around him. He drops deep insights in to things he has never seen before. I did not dislike the character. He has a couple of traits I won't mention that makes him interesting. However, if you were to lay out a scene and ask me how Luca should react, my guess is he would speak some sage advice in one sentence, and then say he has no idea in the next sentence.
I gave Book 1 a 4/5. I give Book 2 the same 4/5. While Book 1 is better, I really appreciate wrapping up the story. There is room for another adventure, but all the main story arcs were closed, and I was left satisfied and never bored. Fans of Book 1 will be pleased enough continuing Cassie's journey to completion.