How often, when reading fsf, do we get into Catholic spaces?
Poul Anderson Three Hearts AndThree Lions The Merman's Children
Nicholas van Rijn
Blog readers will know of other relevant works. Some have been mentioned on the blog, e.g. here.
Emberverse incorporates Catholicism but is not Catholic. One Mind includes many gods and/or one Power manifests both as the Goddess and as the Virgin Mary. Artos, Wiccan, senses Power in a Catholic chapel - but that can happen in our universe.