Horror is a feeling and reaction as much as a genre. Horror fiction may elicit fear and surprise, and contains any one or a combination of the following elements: mystery, gore, dark atmosphere, creeping dread, and unease. Some consider terror a separate genre while others believe it’s an aspect of horror.
No genre has defined borders and that’s perhaps truer for horror than other genres.
Book Riot Horror: Horror book reviews and recommendations—email newsletter available
Thought Catalog (Creepy Catalog): fiction, true crime, horror, and horror-adjacent movies—email newsletter available
The Horror Bookshelf: Dormant, but has an extensive backfile of horror book reviews