My admiration is boundless. It depends on what you mean by spiritual writing.
Writing is a visceral activity, as are all the arts.
As this survey attests, spiritual writing is a pixilated genre, manna to some, dementia to others. Spiritual writing may be confessional, prescriptive, satirical or polemical. But it always engages that elusive realm of human existence lying just beyond the reach of the test tube, the opinion poll or the psychiatrist's couch, where we encounter the great mysteries of good and evil, suffering and death, God and salvation. Nowadays, the genre basks in the sun. Sales of spiritual writing easily outstrip those of other recent nonfiction success stories, like nature or travel writing.