So what clues does CNN rely on? The researchers categorized three matters: color, objects, and text. For example, CNN associated white with “Self-help,” and dark colors for “Science Fiction & Fantasy.” If two people stood in close proximity, CNN guessed “Romance.” If people were illustrated, it predicted “Comics & Graphic Novels.” While “Mystery, Thriller & Suspense” tended to have a similar color palette and image content to “Romance” and “Science Fiction & Fantasy,” CNN distinguished them by their texts; “Mystery, Thriller & Suspense” books usually employ large, overlaid sans serif text.