Daemon wasn’t particularly happy when new neighbors moved in next door. He was even less happy when one of them was a girl his own age. And when that girl ended up being gorgeous? Well, unhappy didn’t really cover his feelings on the situation. He had secrets to keep, namely that he wasn't human. That secret would quickly become far harder to hide if humans moved in next door. He needed to scare her off. If she stuck around, it could hurt him and his sister, but the more time he spent around her the harder it was to stay away. He had known from the day she moved in next door she would be trouble for him, and he really had to stop liking that trouble.
This entire story makes the first one make a lot more sense. If you enjoyed Obsidian, you might love Oblivion. It would most likely make Daemon make a lot more sense. He’s confusing in the first book, but his actions are contextualized throughout this book. His love for his sister and his protective nature and his developing feelings for Katy and how hard he fights against those feelings makes him such an appealing protagonist. It’s really cool to see the story through his eyes and some scenes that weren’t originally seen. Getting inside his head to see what he was thinking a feeling was totally interesting throughout the book and I think it’s absolutely worth a read.