I think Ink Exchange by Melissa Marr is a little darker and for slightly more mature readers than Wicked Lovely (due to more discussions of sex, drugs, and debauchery), but I think I liked it better. It's true that you don't have to have read Wicked Lovely first to understand Ink Exchange, but I'd recommend it.
Aislinn's friend Leslie is not as tough and free-spirited as she appeared in Wicked Lovely. She is dealing with some difficult emotional issues related to her mother's abandonment, her father's inability to provide for her family, and the fact that her brother offered her up sexually to his drug dealer to support his addiction. She decides she wants to get a tattoo to reclaim control of her body. She finally decides on one in Rabbit's (the tattoo artist) special book. What she doesn't realize is that the design she's chosen is that of Irial, king of the Dark Court. She also doesn't realize that the ink Rabbit uses for her tattoo is mixed with the blood and tears of Dark Court faeries. Once she begins the process of getting the tattoo, she gets drawn more and more into the faerie world.
Okay, that's the short plot description. Read on for more (with possible spoilers).
Now that Donia is the Winter Queen and at peace with the Summer Court, the Dark Court fey don't have enough jumbled emotions upon which to draw sustenance. So Irial seeks out a mortal for an ink exchange. This will allow him to feed off the emotions of humans and sustain, temporarily at least, the Dark Court. He begins to feel attracted to and protective of Leslie, and she feels attracted to, scared of, and, of course, connected to him more and more. At odds with this, Leslie has always been attracted to Keenan's advisor, Niall (who used to be part of the Dark Court; he and Irial have a history). Niall has been shadowing Leslie in order to protect her, per Aislinn's request, and he is increasingly attracted to her. However, he knows that he should not act on his feelings because Aislinn doesn't want him to (she doesn't want Leslie brought into the faerie world) and because his skin is addictive to humans, and if he ever leaves them, they will suffer and die from withdrawl. But since Leslie comes on to him, he's concerned for her safety since Irial is showing such an interest in her, and because her tattoo is bonding her ever closer to the Dark Court, Irial finds it more and more impossible to resist pursuing her.
What I liked in Wicked Lovely and what I love love love in Ink Exchange is how all of the characters are not merely good or bad but have elements of both and you can root for all/both of them. Even in this love triangle with Irial and Niall, you can see her with both of them. Also, the covers are so amazing! I am in love with both of her book covers. (Wicked Lovely is my computer background.)
I can't wait to talk about the ending with someone!