After all that happened in Onyx, that tragic ending and the return of a long-lost character, how could Jennifer satiate her fans in Opal? Well, she does it by making us swoon even further with a sweet, caring, considerate Daemon. And she kicks our hearts with another heartfelt ending that will leave you shouting "NOOOOOO!!! That's it?! Why?! Why?!". 
 I'll admit, after all that happened in Onyx, Opal was a bit more relaxed in the sense that not as much happens, action-wise. I wouldn't say it was lackluster or anything, because Jen's writing is as entertaining and flawless as ever, but it wasn't as epic as I was hoping. Most of Opal revolves around the characters figuring out how to save Bethany and others like her, getting Dawson back to a semblance of normal life, Katy learning to harness her powers her and deal with the ramifications of her past actions, and the development of Katy and Daemon's relationship. The pacing was excellent, as always, and I was deeply engrossed from beginning to end, but I think it had more to do with my investment in the characters and the plot as a series, rather than the book itself, which was steady and even uneventful at times. 
 Daemon does a complete 360 and you really get to see a whole new side to him. He truly cares for Katy and does a lot to show it. That's not to say you don't get a nice dose of Daemon smartassery here and there, which we all love, but you also get a lot his sweet side and a few moments where you just want to hug the guy, he's so lovable. He's definitely the highlight of the series. 
 Opal was a great addition to the Lux series and it definitely left me wanting more, as does all of Jen's books. Like others have said, that ending kind of ripped at my heart a little, although I kind of saw it coming. 
 Though it's not as riveting as its predecessors, I still loved it and can't wait to read Origin.