On Book Cave, we use the ebook content rating system from our database of rated books found on My Book Ratings, or the MBR system. MBR ratings can be assigned by the community (readers, authors, and publishers) or as an official rating called Rated by MBR (meaning we read the entire book and rated it officially). These ratings are a somewhat like movie ratings, and they're divided into seven groups: All Ages, Mild, Mild+, Moderate, Moderate+, Adult, and Adult+.
Books are assigned ratings based on seven categories: crude humor/language, profanity, drug and alcohol use, kissing, nudity, sex and intimacy, and violence and horror. Within each of these categories there are levels of varying degrees, which are assigned a rating (All Ages, Mild, Mild+, Moderate, Moderate+, Adult, and Adult+). The book itself is assigned an overall rating in relation to the highest level across all categories, and the individual rating level for each of the categories is also listed in the daily deals email and on the book's page.
For more information, check out these examples or click each icon below to learn what would make a book “earn” that rating.