Honest answer from someone who writes the genre: it splits in two. The loud, popular end is Haunting Adeline (H.D. Carlton) and Captive in the Dark (C.J. Roberts): obsession, captivity, dubious consent, explicit. The quieter end runs on atmosphere, where the danger is a mood, not a plot device. Which half do you need? I write dark romance myself (EN/SV), so I am not neutral.