I am surprised no ones mentioned him yet, whilst I read a wide variety of genres and different authors, there is something that is very special about Terry Pratchett. I especially enjoy his philosophical views and various theological ideas. Not to mention the fact that his writing career has spanned decades and there are literally tonnes of books to keep me occupied or entertained.
That aside, if I really was stranded on an island. I would probably want to have books written by Ray Mears.