I have finally finished this book and while it was definitely a star up from Beautiful Creatures, I can't say that this is a series I will keep my eye on. 
 Things I liked about Beautiful Darkness: 
 + I liked that Link, and new character "Liv", got quite a bit of screen-time in this story. I found Link's humor and dialogue to be rather amusing and it certainly kept me going when it came to reading. Liv was also another interesting character. She answered whatever questions Ethan/Link/readers might have and I really got the sense that I understood the story better with her around. 
 + The action. I have to say, there was quite a bit of action going on throughout the novel and it certainly made it easy for me to continue reading. 
 + Twists and turns; they certainly did come fast and furious in here. 
 Things I didn't like about Beautiful Darkness: 
 + Ethan and Lena's relationship. Obviously, they go through a tough time in this one and are apart for quite a fair bit of the novel. I just couldn't stand how Ethan was just pining and worrying and just going crazy about Lena. I'm sorry but I cannot actually see a guy having that kind of behavior/thoughts, no matter how much he loved a girl. 
 + Plot points. Seriously, every time Ethan and company got into an impossible situation, something miraculous would inevitably happen to save them all. How lucky. But really, no one is that lucky. 
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 The ending just screams out for a sequel. I'm not sure if I'd read it but hey, maybe I might be cajoled into it.