Sci Fi novel with atheist/time travel themes main characters name starts with J, round buildings/windows???

[Kaligirl12]

Looking for the title/author of a book I read as a kid in the mid 1990’s. The copy I had was a paperback with a blue cover that I got from the public library. Possibly YA, novel about a man who ended up in another world (planet?) and had to adapt to a new way of life.
There were religious possibly atheist themes. Title may have had something to do with Light, main characters name maybe started with a J- Jeremy?
Buildings in the world were round, round windows?
Please help!

 

[TomMazanec]

If you can remember the cover, try Good Show Sir - Only the worst Sci-fi/Fantasy book covers
I've found a few that way.