Onyx picks up right where Obsidian ends - with Katy, Daemon and the other Lumins having defeated the latest Amun threat. And it seems like the arrogant alien has turned over a new leaf. Daemon is now romantically pursuing Katy and whilst she's not immune to his charms, she's slightly put out. She's convinced he's only interested because of the connection they share after he healed her from her near fatal injuries after the Amun battle. Katy wants the kind of relationship her parents had. "Undying love. Powerful. True. [Something] a whacked-out alien bond [just] couldn't do [for her]." 
 Things between the two of them don't get any easier when the new guy in school, a surfer from California, Blake Saunders asks Katy to a party... and stumbles upon her secret. That ever since Daemon healed her, she's been starting to possess alien powers that she can't control. 
 With the Department of Defense (DoD) arrive in town and the Amun show up again, it seems that Katy has more to worry about than ever before... 
 I'll admit it. I'm a little bit of a Daemon fan girl. I liked him in Obsidian and he didn't disappoint in Onyx. Although I do wonder just what it is he has against computers - they don't seem to stand a chance when he's around Katy. The bad boy alien shows off his jealous side and started to become more than just the angry boy-next-door. Despite all the arrogance, I could tell that he really does care about Katy, and not just because she possessed the information to out him and his family to the authorities. 
 Katy, as many main characters in the books I like to read have a tendency to do, doesn't always think before she acts. Even when it's likely to put her at a disadvantage in a life or death situation. But this time around I found myself wanting her to succeed. 
 Blake was a great new addition to the story. A romantic rival who brings more than just Daemon's jealousy to the plot. He's interesting and I enjoyed learning all about the Lumins and the connections between certain aliens and humans. The DoD added an extra element of fear and suspense to the novel. I liked that the supernatural beings (not including the Amun) were the good guys and the human department are what the characters should be fearing. 
 I enjoyed all the drama that occurred in this book. There's suspense and action but it's more than just drama. I liked how the relationships developed. This book is exciting. Just when I thought everything was wrapping up, something new happened and I was thrown right back into everything. 
 There's new characters who are more than they seem and a sinister plot that's really ramping up with lots too look forward to in the next instalment of the Lux series.