I strongly recommend that anyone who likes critically acclaimed, yet enjoyable, science fiction to try out (if they haven't done so) Gardner Dozois' The Year's Best Science Fiction anthology series. It has now reached Volume 26. I have been reading science fiction novels, magazines and anthologies for more than 20 years and I constantly find Dozois' annual anthology to be the most satisfying and rewarding.
If you want a story that explores humanity and especially one that looks at sentience, I really enjoyed the first story in Dozois' 24th volume entitled "I, Row-Boat" by Cory Doctorow. The title which seems like a spoof of the classic I, Robot is really appropriate once you've read the story.
I think the best SF novel I have read is Alastair Reynolds' Pushing Ice. It's the most mind-boggling book I have ever read. I think it gives a new meaning to the word "epic". You may need a little patience though during the first 250 pages which I found a bit slow.
As to whether believers should even read SF, I'm not too sure if that question is really that naive or narrow-minded. When I was erm... younger :D, I found some SF stories very troubling to my faith. Twice in my life, I vowed off SF and read mystery and classics instead. Fortunately, my faith is a lot less shakable now and I'm back on SF for good.