There are several similar series in the "erotic thriller" or "paranormal romance" genres that use the volume-based naming convention.
Modern interpretations of Greek nymphs (nature spirits). Xotic Nymphs Volume 3 2016
High-contrast, "exotic" locations (forests, waterfalls), and often stylized costumes or body art. 2. Erotic Literature & Short Stories There are several similar series in the "erotic