The Left Hand of Darkness by Ursula K Le Guin
Love doesn't just sit there, like a stone, it has to be made, like bread; remade all the time, made new
Two people, until recently strangers, find themselves on a long, tortuous and dangerous journey across the ice. One is an outcast, forced to leave his beloved homeland; the other is fleeing from a different kind of persecution. What they have in common is curiosity, about others and themselves, and an almost unshakeable belief that the world can be a better place. As they journey for over 800 miles, across the harshest, most inhospitable landscape, they discover the true meaning of friendship, and of love.
'A rich and complex story of friendship and love' GUARDIAN
'It's a giant thought experiment that's also a cracking good read about gender' Neil Gaiman