Chosen (Slayer, Bk. 2) by White, Kiersten

Nina continues to learn how to use her slayer powers against enemies old and new in this second novel in the New York Times bestselling series from Kiersten White, set in the world of Buffy the Vampire Slayer. Now that Nina has turned the Watcher’s Castle into a utopia for hurt and lonely demons, she’s still waiting for the utopia part to kick in. With her sister Artemis gone and only a few people remaining at the castle—including her still-distant mother—Nina has her hands full. Plus, though she gained back her Slayer powers from Leo, they’re not feeling quite right after being held by the seriously evil succubus Eve, a.k.a. fake Watcher’s Council member and Leo’s mom. And while Nina is dealing with the darkness inside, there’s also a new threat on the outside, portended by an odd triangle symbol that seems to be popping up everywhere, in connection with Sean’s demon drug ring as well as someone a bit closer to home. Because one near-apocalypse just isn’t enough, right? The darkness always finds you. And once again, it’s coming for the Slayer.