@PostImpressionism there are 16 novels, including 4.5, 7.5, and 11.5, so 13 "main" volumes, although the .5 volumes are still necessary, especially 7.5 and 11.5
@MolaCola
You are better off reading the original light novels.
But between the anime and manga, the anime as Ayanokouji does not show as much emotion. Although he isn't as heartless as portrayed in the anime.