I am not a SF fan in particular... I enjoy LoTR, it is the one book that I will re-read over and over again my entire life. But I have read few others in the genre. I don't seek them out over others. My interest vary widely... For a hoot, I love Hitch-hikers Guide to the Galaxy... It is kindof a sober version of Fear and Loathing in Las Vegas.
I like John Grisham, but he probably doesn't fit your definition of detective stories. He is on the other shelf called legal thrillers... I would hate to think we can't talk about books because they aren't on the right shelf... I don't even know what shelf to put Tom Clancy on...