I've written in this genre. One is a song or poem about spiritual thoughts based on the Big Bang and Evolution. I'm in the middle of writing an article about spiritual atheism. It's more factual than personal but it does reflect my personal interest. I've written religious satire in a piece of fiction called "Marcia Goes to Hell." and an in-progress historical religious fantasy. I've written critiques of spiritual pieces that I thought were misstating facts; I've argued the logic of pieces that invited debate; and I've positively critiqued pieces that I personally disagreed with but thought were well argued and well written.
One thing to keep in mind about spiritual writing is that it is potentially controversial. Most people won't blast you for it, but most won't comment if they disagree. I'm probably a rare exception to this rule but I hope I am always respectful. Even I don't respond if I think the writer is so far out that a dialogue is impossible.
My suggestions for spiritual writing are
1) get your facts straight
2) stick to why you believe what you believe and how you benefit from your beliefs rather than criticizing other belief systems
3) try to be clear about the difference between your religious opinions (of which there is much disagreement and little to no hard evidence) and generally accepted fact.
4) if your belief system allows for doubt, multiple interpretations, admits we don't really know the source of(the truth behind) our spiritual longings, or admires a variety of spiritual systems, that makes for good writing and reading.
5) expressing spirituality through fiction can sometimes work better than essay style writing.
Marcia
