The book that Albie is reading while he's waiting for Portia is "The Architecture of Closed Worlds," by Lydia Kallipoliti. It's about closed, self-sustaining systems, which could metaphorically describe the White Lotus resorts.
What Guiseppe told Mia regarding the church they sneak into being deconsecrated is a lie otherwise there wouldn't be any lit candles, table cloth on the altar, etc. in the church.