This classic sword-and-sorcery novel contains a rather unusual scene involving a threesome. The hero has made a romantic tryst with the mysterious woman he's been pursuing. He's surprised when she turns up together with her faithful maidservant, and even more surprised when she tells him what the deal is. He can kiss HER all he wants, but he has to do it while embracing the other chick. This unorthodox arrangement works out surprisingly well.
It turns out later that the mysterious woman had her reasons. I didn't guess them ahead of time, and neither did the hero!