Two 20 year olds who have been in love since they were 11. The boy is suicidal, but they never really explain why. The girl is obsessed with him, I think she loves him out of habit because she alternately loves him, hates him, cheats on him, feels terribly guilty, is angry at him for wanting to die and simultaneously wishing for the relief it would bring.
It is set in the late 70's, has sex between practical strangers, drug use in varying degrees.
The guy dies in the end. It sounds like I'm ruining it, but you find out in the beginning.