Evil Librarian by Michelle Knudsen

 evilCyn is initially thrilled when her teasing BFF Annie finally shows signs of infatuation, until she discovers the object of Annie’s affections is the new school librarian. Mr. Gabriel’s attention to Annie unsettles Cyn and readers alike. At first suspecting the creepy Gabriel is a manipulative and inappropriate authority figure (awful enough), Cyn learns that he’s a horned and winged demon. He wants brainwashed Annie for his human consort, when he returns to his realm to fight for the throne with the life essence he’s poached from her classmates.

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