The film is stark, violent, and deliberately slow. It is less about the physical acts and more about the erosion of identity. Richard loses his grip on reality, and the audience is dragged down with him. It is not a "good time" movie. It is an experience.
If you watch L'Histoire de Richard O. , manage your expectations. You will not find arousal. You will find loneliness, neon-lit Paris streets, long silences, and a protagonist who seems trapped in his own skin. That, perhaps, is the point.