For decades, I'd had an idea about this book, completely based on the title. I wasn't close.

It's definitely spare, wasting little time not exploring the concepts that Le Guin wanted to, even though it dragged (I thought) just a little during the Long Trek, but still very good.
A fascinating premise, which (as the best SF does) allows us to turn the lens on ourselves, examining what it means to be us - to be either One or the Other (as well as the more obvious male/female schism).
It's clear why this is a classic - add it to your list.