Simon & Schuster began tracking a newer subgenre of horror called "liminal spaces" in 2025. Liminal spaces are physical locations or emotional states of transition when individuals are in-between one place, time, or identity and the next. The subgenre started growing in popularity when some Tiktok posts went viral, and Audience Insights Senior Manager Anna Hall saw very active Reddit threads and google search volume showing steady interest. Popularity has continued with the movie "Backrooms," she says, which is a typical liminal spaces horror story.