This book has a teenage main character who does things most teens do. Okay, most teens aren't stalked by fallen angels and their crazy jealous exes, but the other things going on in the book are typical YA. There are biology labs, shopping trips with friends, crushes, mean girls, and exciting trips to arcades and amusement parks. The characters, conflicts, themes—and most importantly the vocab, voice, style, and tone—are all meant to ring true for teen readers.
As for those fallen angels and their crazy jealous angel ex-lovers, that's where the fantasy genre comes in. There are different kinds of fantasy, and Hush, Hush is what's called low fantasy, which means the story takes place in the real world with magical, paranormal, or supernatural features tossed in. Bust that term out at the dinner table to baffle your siblings and impress your parents.