This might come off as a bit of a rant, but I feel like the line gets blurred so often in conversations that it's worth untangling. Literary erotica, at its core, treats the sexual act as a primary lens for exploring character interiority, power, or philosophical ideas. The prose is often denser, more metaphorical, and the emotional arc can be... messier, less concerned with a guaranteed romantic payoff. Something like 'The Story of O' is an extreme example, but even Anne Rice's early erotica under pseudonyms had that contemplative, almost gothic weight to it. The sex isn't just a spice; it's the entire meal, dissected.
Traditional spicy romance, on the other hand, uses sexual tension and release as a key narrative engine driving toward a specific emotional destination—usually a committed, loving relationship. The heat level can be just as high, but the context frames it within a journey of emotional safety and ultimate partnership. The difference is in the ultimate destination: one is often an exploration of a facet of desire itself, while the other is a crucial milestone on a romantic quest. I've definitely shelved books thinking they were one thing and ended up with the other, which isn't bad, just a different headspace.
To be fair, my shelf holds both, but I reach for them at different times. The literary stuff is for when I'm feeling intellectually curious about desire, and the spicy romance is for when I want that reliable emotional catharsis wrapped in a steamy package.