My favorite author is Orson Scott Card. I liked him for a long time before finding out that he is Mormon and there are Mormon themes in many of his books. I would never have guessed, though I did notice (and appreciate) that he did have some religious characters portrayed well (not all that common in science fiction).
Here is an excellent interview where OSC is asked about the Moemonism in his writing:
http://mormonartist.net/issue-13/orson-scott-card/
I loved his perspective on the topic and it explains why I've been able to appreciate his writing without ever being particularly fond of Mormonism
Lee