Asimov is an incredibly broad writer. He has some stuff aimed at younger readers, but still managed to be uncomfortably sexist with the Norby novels. Robots of Dawn involves sex with robots. I'm not that familiar with the Foundation series but I've heard Foundation's Edge uses sex to drive the plot.
I couldn't finish Foundation, after making it nearly all the way through the book and finding the only woman in the story was someone's secretary. It just felt like very, very dated and boring writing. I don't feel like all his stuff has aged so poorly, either.
