Nothing makes a book burn hotter than a villain you want to win. The best sex demon novels get that the threat isn't just physical, it’s psychological—the ultimate corruption is wanting it.
My top pick has to be 'Kushiel's Dart' by Jacqueline Carey. The antagonist isn’t a literal demon, but Melisande Shahrizai might as well be. She’s this devastatingly intelligent, ice-cold beauty who uses seduction as a geopolitical weapon. The tension is all in the mind games; you feel the protagonist’s terrified fascination. It’s less about monster-fighting and more about the slow, exquisite erosion of will.
For a more literal take, Sierra Simone’s 'Priest' features a character grappling with a demonic temptation that’s explicitly framed as a seductive, taunting force. The conflict is internal, which I always find more compelling. The ‘demon’ is the voice whispering why the rules shouldn’t apply, and the setting—a man of faith—makes that seduction so much more potent. The heat comes from the battle between sacred duty and profane desire, not special effects.
I’d avoid anything that treats the demon as a simple monster with benefits. The magic is in the ambiguity, the moments where you, the reader, start to question the protagonist’s resistance. That’s the real seduction.