I suppose the Bible? It's dramatic and long and you would have lots of soft thin pages to use for kindling or TP. (San Francisco, CA)
It depends on how long I was stranded on the island. All kinds of books and lots of them. Fiction and non-fiction. (Chicago, IL)
Grace Paley's stories, full of life, activism, women
Chris Adrian's Children's Hospital suits the situation
James Baldwin's essays
EB White's non-fiction