King of Death by Lily Mayne

Everything should be fine. The Brid is dead. I’m the new seelie king. And Lonan is with me, safe from the unseelie queen—his mother—and terrible brothers.
But it’s not fine. Nothing is fine.
I can’t seem to let go of my old life, even as this new one—and my new responsibilities—overwhelm me. Something is wrong with Lonan—he’s closing himself off even more, he’s quiet and distant, and every day the rift between us seems to get bigger, no matter what I do.
I know he wants to go and take his crown. I know he doesn’t feel right here, in this place that’s too hot and too crowded and too different from his home. But I can’t bring myself to let him go. I’ve already lost everything once. I can’t stand the thought of losing him.
But something is happening to me, and I don’t know how to stop it. I can feel myself changing. Becoming something uglier, darker, further and further from who I once was.
Lonan is the only thing stopping me from getting swallowed up completely by whatever now possesses me, but my desperation to keep him close just seems to be driving him further away. And that scares me more than anything.