Honestly the long haul, associated beliefs are a factor.
Like, if you can change someone from more prochoice to more pro life, then usually religion will follow. Visa versa for atheism. (It gets deeper, but I'm going to avoid more... controversial side issues in this post because I don't feel like arguing about any right now lol).
But you yourself could reflect on such concepts. Consider the real points that demand these contentions. I mean in a sense if someone is pro choice enough, then they won't ever accept a "normal" amount of God discussion, because they won't want to sell their things and follow Him (ie their pro murder ideals).
But if they are converted into having sold their stuff first, often the God part has less obstacles.
Anyway, as to some books, I would suggest an intro factor that is written by an Anglican who is borderline Hindu lol.
Science and Spiritual Practices
It does have a univeralist tinge and isn't specifically evangelizing for God/Christianity, but it is a door opener for at least the concepts of Spiriutality from a scientific and effectively materialistic standpoint.