Parents need to know that "Slayer" is the first book from the world of the "Buffy the Vampire Slayer" TV series and movie written by longtime Buffy fan/bestselling author Kiersten White ("And I Darken" trilogy). It helps to have watched the TV series to keep up with some of the characters and lore that pop up throughout the story. Expect demon-against-Slayer violence with many demons ending up dead (some by decapitation). Humans who die do so more quietly, in their sleep. Trauma from the past bubbles up often: the loss of a father and many family friends, a house fire, a girl whipped by her own mother. Caged demons are tortured, with one slowly skinned alive. Other mature content stays pretty mild: a bar scene with some beers, some minor swearing, a couple of kisses, straight and LGBTQ. When the main character, Athena, discovers she has supernatural abilities as a Slayer, she doesn't forget that she's always been a healer and protector. She tries to find a way to be both.