I wasn't ready for this book when I first read it as a teen. At least, that's what I think now. Most of it went over my head and I found it to be, overall, boring in parts and frustrating in others, as I failed to really grasp the politics going on. Basically, it's a sci-fi futuristic story about an envoy from a united-planets kind of organization going to a foreign world that was long-ago colonized by humans who were then forgotten for centuries. They have evolved into different beings that basically don't have a gender except for a few days during the year when they are ready to mate and have children, and they can take either a male or female role during that time. Although the people look like our envoy he finds their culture very strange and they in turn see him as an alien and a freak. Even their history is vastly different from Earth's, as the lack of gender roles and identity as we see it shaped their society very differently. I remember some specific incidents where the envoy got into awkward situations from misunderstanding social cues, and other scenes which described the various arrangements of family life, but a lot of this book was a blur to me and I didn't really understand much of it. I'm making a note of it here as I do want to revisit it someday and see what a new impression will bring.
See some of the reviews linked to below for a much more comprehensive description.