Not sure if I agree with the christian references being incidental ... the first book is literally a retelling of the The Canterbury Tales, all the characters are on a pilgrimage. there are a bunch of religious groups with at least one being central to the story, there are cross shaped parasites that grant eternal life.
I still think you can enjoy it without caring much about religion.
>there are cross shaped parasites that grant eternal life
Without giving away any spoilers to the books, the parasites are only that on the surface. If anything, the books present a wary picture of religion, especially the last two Endymion books, but also a wary picture of technology.
> the first book is literally a retelling of the The Canterbury Tales, all the characters are on a pilgrimage.
As we have both read the books, it's notable that you associate pilgrimage with Christianity. This illustrates the point.