I highly recommend Onyx. 
 ***** 
 Kat and Daemon are H.O.T.T.E.R. than ever. The action scenes didn't hurt, either. :) Yesssss! 
 But let me tone down a little with my fangirling ;) I have some issues with Onyx, especially with Kat's low self-esteem, but who cares. I am in love with the story, in love with Kat and Daemon, in love with Daemon, period. Sexiness doesn't even begin to cover the awesomeness of Onyx. =) 
 Daemon is still stab-worthy here, but his mask of arrogance and indifference started to slip in front of Katy. And how refreshing it was to read Daemon as this hot alien exhibiting human traits like want, confusion, and jealousy! The scenes where he intentionally calls the new guy with different names every time were hilarious. Take that, surfer boy. 
 The scenes that made me the ultimate Daemon fanatic are: (1) The first gift he gave Katy during lunch (i thought it was surfer boy!); (2) His reaction on finding out Katy's went out with surfer boy (after spending the night together talking and snuggling); and (3) He let Katy into his room for the first time (turns out Daemon's not a complete scumbag after all!). Daemon is really the star in Onyx. His character developed from this egotistical jerk in Obsidian to this unconsciously-sweet-but-still-a-smart-ass guy. 
 As much as I would like to not discuss Kate, it is imperative that I tell you this: Katy started out strong. But her relentless doubt over Daemon's real intentions for her was over-the-top frustrating. And to trust a new guy over Daemon? Unbelievable. But she was resentful of her actions in the end. and the new Katy was bad-ass! forged from the fires of destruction and grief, Katy came out better, stronger, and no-longer-a-pushover girl who's now Daemon's equal in every sense. :P 
 The interchanging of mood from funny to hot to serious was unobtrusive. A lot of LOL moments. Several swooooon moments! But definitely the alien plot (plus more fight scenes) was entertaining. 
 The Lux series will be one of those series that i will never,ever get tired of giving 5 stars (despite the holes i've seen or will see). They are such feel-good books! Thank you, Ms. Armentrout, for letting me escape reality even for just 6-8 hours. *winks* 
 Obsidian ignited a spark. Onyx fanned the flame. Katy and Daemon's fire will ROAAAAR to life like never before! 
 Hurry up, December! Must. Read. Opal. Immediately.