Fascinating . . . I love Tiptree's work! I haven't read Joanna Russ, do you have a recommendation for one of her best works?

If you can track down a copy of her Alyx book of short stories, that is actually what I would suggest starting with. Her short stories are as amazing (she published three collections total) as her novels, but this one in particular is from early in her fiction writing career, and as you read she is moving further and further into more and more mindbending ideas as well as her approach to nonlinear storytelling. Otherwise, The Female Man or We Who Are About To.