Start with high-confidence religious essays books, then narrow by subgenre or adjacent topics.
The Weight of Glory
C. S. Lewis
Holy the Firm
Annie Dillard
The Enlightened Mind
Stephen Mitchell
Waiting for God
Simone Weil
Original Sin
Alan Jacobs
Risks of Faith
James Cone
Angels & Saints
Eliot Weinberger, Mary Wellesley
Balm in Gilead
Timothy Larsen, Keith L. Johnson
Miracle on 10th Street
Madeleine L'Engle, Diana Butler Bass
Heretics
G. K. Chesterton
What's Wrong With the World
G.K. Chesterton
Orthodoxy
G.K. Chesterton, Trevor O'Hare
