I read Stranger in a Strange Land in my youth and it was mind-blowing. The unnecessary Lewdness was nice in puberty but looking back today it's more like a thing of its time thing...

I, too, read it when younger and thought there was a lot of sex in Stranger in a Strange Land until I read Dahlgren where there is a lot less thinking and talking about it and more just step by step descriptions of every act, and that book came about fifteen years later.