I can't think of anything exceedingly obscure. Perhaps Rynosseros (Terry Dowling) might barely qualify amongst the broader public, but I daresay the SF-interest amongst this group might possibly deny its obscurity.
So, instead, I'll go for a non-obscure writer's perhaps slightly obscure first novel (though it won the Miles Franklin Award and was made into a movie with Barry Otto, so I'm pushing it). Anyway, the book is not Oscar and Lucinda or The True History of the Kelly Gang bur rather Peter Carey's Bliss.
Bliss is about a man blissfully believing he is living the Australian dream, until he dies for nine minutes and wakes up in what he believes is literally Hell. His wife is cheating on him, his son is selling drugs, his daughter is whoring herself to buy those drugs, his business partner's an arse, and his car is sat on by an elephant. Then he meets Honey Barbara...and you will never look at honey in the same way again. He is to die twice more.
It is one of my favourite books, and the movie is also worth watching (I believe reading the book beforehand improves the movie. Barry Otto is brilliant in the lead).
Sorry, it's not that obscure, though perhaps enough so amongst a predominantly non-Australasian crowd. I'll have a look through my bookcases tomorrow for something more obscure.