Get on list for Catholic bookstores
If you write books that are clean (no swearing, no spice, no excessive violence, etc.) and do not directly contradict Catholic doctrine, you can get your book on the “list” that parishes and church libraries can order from. Almost every Catholic church has a library, so theoretically, you could sell some books!
The Catholic church opens this list only 4 times a year, and only for 24 hours. THE NEXT TIME IS SEPTEMBER 14.
Here’s the thing. For trad published books, your publisher should submit your book.
For indie authors, you must provide proof that your book has been professionally edited and they will decide if your book is up to the standards of a trad published book.
EDIT TO ADD: This is the Catholic Writers Guild’s “Seal of Approval.” This puts the title on a website that churches and parishes can order from. Apply through the Catholic Writers Guild website. Books don’t need to be Catholic oriented, they just can’t have anything that would be considered against Catholic teachings.
FOR EXAMPLE: my current WIP features characters at the United Methodist Church, but it’s mentioned that some characters go to the Catholic church, which will be featured more prominently in a future book in the series. But there’s nothing in there that is anti Catholic or specifically goes against their teachings. In fact, the youth groups from both churches volunteer to distribute flyers for a community event. So my book would likely qualify, if it were complete.