Lots of great suggestions involving story craft and the like, so I'll target the "religious hangups" bit with a couple non-fiction books:

• Sentience by Nicholas Humphrey (great to get a perspective on consciousness and sentience that isn't marred with religious doctrine)

• Determined by Robert Sapolsky (a primatologist with a knack for getting you comfortable with the notion that we don't have as free a will as religion tells us)

And just to include a bit of fiction:

• Children of Time by Adrian Tchaikovsky (about life as we know it, or maybe as we don't)

• Fourth Wing by Rebecca Yarros (deals with overwritten cultures. Also dragons.)