re: Any book recommendations on the Greco-Persian wars?

Two that kinda sorta meet your description and are good reads:

Anabasis by Xenophon - about a group of 10,000 Greek mercenaries fighting in a sort of Persian civil war and them trying to get back home. Narrated by the guy who actually led the group.

Creation by Gore Vidal. About a guy who was the grandson of the religious founder Zoroaster who later serves as an ambassador for Darius and at one point is stationed at Athens.

And here is a site which lists a ton of novels about ancient times including Greek/Persian stuff that I stumbled across when trying to recall the name of the Vidal novel:

Historical Novels

Not sure how good any of those are but you can check out the list and see what appeals to you.