Captivate by Carrie Jones

What's on the back of the book:
He smiles. It's a wicked smile. Kind but not kind.
Handsome but dangerous. Feral almost.
I can see why Nick nearly killed him. Nick . . .
I ask again, 'Why were you in the road?'
'I was waiting for you.'

Zara and her friends thought they'd solved the pixie problem. And they had - sort of. They're locked away, deep in the woods. But the king's needs grow stronger each day that he's in captivity, while his control over his people weakens. Who will fill the power vacuum? Astley. He claims he's different. He claims that it doesn't have to be violence and nastiness all the time. Zara wants to believe him . . . until Astley also claims that she's fated to be his queen.
There's no way Zara would ever turn pixie. And she's got good friends who'll make sure of that. Besides, she and Nick are so in love they're practically inseparable. But when the very thing Zara most wants to protect is exactly what's at risk, she's forced to make choices she never imagined.

A piece from the book:
He moves just a little bit and my fingers fall off of his wrist. He stands up and just walks away, shoulders straight, but different than before. There's something humble about them almost. I don't know. I don't understand anything.
"Hey! Do you have a name?" I call after him. My voice is weak but it stops him.
He turns around. This time he gives a full smile, revealing perfect teeth, white and even. His whole face transforms into something beautiful, the same way Nick's face changes. "Astley."
I touch my feet to the ground, repeat it "Astley?"
He lifts his shoulders and smiles. "We do not have the opportunity to choose our own names, unfortunately."
"What does it mean? Does it mean something?"
"Star." He turns and disappears into the woods like he was never there at all.
"Wait! Can you tell me about Valkyries?" I yell after him.
There's no answer. I collapse onto the car upholstery and watch my skin gradually turn back pale again, almost like nothing happened. Almost.
"I will never kiss you," I whisper. "I will never kiss anyone except Nick."
Of course, nobody hears.