Adult Books, I Don't Understand

Hello! Some scandalous cover art here, for two different editions of the same novel, Succubus. The original edition is below, Lolita-esque model, pub'd 1970 by Dell Books. Above is a later '70s reprint under a pseudonym - Irving A. Greenfield just not the most tantalizing of author names - complete with reference to the almighty Exorcist. I'm gonna side with the dark-fantasy, Heavy Metal-esque