Onyx is not my favorite novel thus far in the Lux series. It still has those Twilight elements, and it has a twisty R&J element as mentioned by Matthew: View Spoiler » One cannot survive if the other perishes.
Honestly, I don't mind if a book is a similar copy of another book, as long as it has it's own original elements as well. Onyx definitely starts breaking off into it's own unique direction (always a plus), with the R&J element mentioned above and others I can't remember off the top of my mind (I remember the important main details of what happens, okay?).
But I had other problems with Onyx:
DaemonIf I don't like a guy character in the first novel, I usually like him by the second. But I do not like Daemon and that poses a problem if I continue to read the next book in the series, because he's a main character. He's not minor like Ash, who I'm actually warming up to. And it really sucked View Spoiler » when Adam died. Why the nice twin? Why not the evil twin?
Daemon is like a stalker, always tailing Katy because "it's for her protection." It's really annoying. I don't see Will Herondale or Jem Carstairs from The Infernal Devices following Tessa around 24/7 to "protect" her, do I? Noooo. And in the 1800s, women didn't usually walk around on their own outside of the house.
KatyShe's more of a damsel in distress. The first book? It's fine with me. Heroines definitely need some assistance here and there. Always? Um... no. I'm going to have to agree with others though: Katy is definitely a frustrating character and is focusing more on her feelings with Daemon and Blake than other stuff throughout the majority of the book.
Katy and Daemon posing a problem for me is a huge no into going further into the series. To my knowledge, Origin, the fourth novel, is in both POVs. See how it causes some conflict for me?