Another solid 3.5 for the sequel. I was very hopeful for how this one would play out - thinking it had the potential to be better than Obsidian, but a number of the conflicts that ended up keeping Katy and Daemon apart throughout most of the book, were based on misunderstandings and not talking to each other - which is not a trope that I like. I also think this book could have benefited from some of Daemon's POV, as there were times when his behavior wasn't as understandable to me as in the first book.
Overall though, an entertaining read that I finished in two sittings. I will definitely be moving on to the next one.
I should mention that Onyx, like Obsidian, ended with a cliffhanger/lack of closure. This is yet another device that I don't appreciate and I am a little worried that the author will continue doing it throughout the entire series, which, I believe is planned to be 5 books. Based on the description for the 4th one though, I'm pretty sure the 3rd is a cliffhanger, so I'm not as excited about it as I could be. :(