While I believe that all authors incorporate their beliefs into their books to some degree by the act of creation itself, some do so deliberately to promulgate their beliefs (Ayn Rand, Terry Goodkind). Only when doing so affects my ability to enjoy or learn, will I allow an author's beliefs to affect whether or not I will read their books. If an author keeps their works generally free of "preaching", I'll read them regardless of their beliefs and how they express them outside of the books I read.