I remember enjoying Vonda McIntyre when I was in High School (possibly Jr. High.. so may books so many years ago. I inhaled the library.) IIRC she does touch on relationships/sex but nothing graphic. My favorites were
Dreamsnake and
Superluminlal. She self-pubs her old titles over on
Book View Cafe where 95% of the price goes to the author.
I also remember liking the previously mentioned Patricia A. McKillip at that time so a second to that recommendation.
Cygnet and the Firebrand,
Forgotten Beasts of Eld,
Moonflash.