Erotica, like any genre of writing, should adhere to all the rules and techniques that guide us as writers or readers, regardless of form. But unlike other genre, erotica has peculiar problems. It tends to be episodic, with the sexual climax supplanting the literary climax. It is difficult to sustain an erotic work at book lengths without creating some excuse or device to string together the episodes, and in most books it reads as just that, an excuse, or gimmick. Because erotica is arousing, it is easy to mistake sexual excitement with good writing.
Language is a problem.
The florid variation becomes both necessary and often comical when struggling to deal with body parts. In my short stories, I've realized that although a number of readers have asked if there were more stories involving particular characters, I have always quit with just one story per character. I'd like to oblige, and I've even wanted to revisit a character myself, but somehow I can't. The conflict in my erotica seems to be whether the characters will get together, and how. I'd like to think that my characters are interesting enough to sustain a short story, but they aren't so interesting that on character alone they could propel a second story, let alone a novel, and the conflict would be a repetition of what had already taken place.