There is quite a bit of sex, and frank discussion of sex, in Stranger in a Strange Land. The problem for me is that while Stranger is easily Heinlein's most well-known novel, IMO it's also one of his crappiest. Give me "The Moon is a Harsh Mistress","Friday", "Podkayne of Mars" or "Farmer in the Sky" any day of the week. SiaSL doesn't hold up.

BUT if you are looking for books that contain some sexual content with a sci-fi bent, by all means pick up Stranger. Hell, read "I Will Fear No Evil" too while you're at it. Another of Heinlein's sex-themed books that also sucks balls.

Instead of stressing about enjoying romance novels, just sprinkle in some other stuff and by all means, keep reading what you enjoy! Isn't that the purpose of reading in the first place? And if you want some sexy fun, pick up some Sandra Brown. I read "Mirror Image" years ago and it's sex every other page, just about.

Have fun!