Erotica can take many forms; visual, the printed word, and in my opinion the best method the example by acting out the sexual act. That way not only is the ideal technique displayed, but the activity in real time gives the observers the sense of participation!
Our heroine is a frustrated wife whose husband is away in the Army on a six months detachment. She answers an advertisement for a model to pose in the nude for a modern Karma-Sutra. She would have to participate in the nude with a male model, but to stop just short of penetration.
It ends up that the man is her, well loved by her, step brother! Now she is caught on the horns of a dilemma, but common sense prevails and they act out all of the poses needed to illusrate the book written by the photographer and his sister.
Unfortunately her stepbrother loses his balance and instead of close sexual contact without penetration he proceeds to do the unthinkable and makes the picture book a best seller, even on all the best sellers list, and all the men who bought the book stated categorically that they didn't buy it for the pictures, but for the written instruction manual itself!
Oh yeah! And the kicker is Our heroine has to explain it to her husband why she couldn't wait for him to come home on leave!