The community rating system for how much sexual content a book contains. Runs from clean (none) to smut (explicit and frequent). Rated in peppers, 1 to 5. 'Spice level?' is the most-asked question in BookTok comments whenever a book gets recommended. Getting the answer wrong is a real credibility hit.
"Before I commit to 500 pages I need to know the spice level. Non-negotiable."