I re-read Ex Machine a few weeks ago, and I agree that the exploration of faith/religion in this novel is quite potent. Interpretation is both a strongpoint and weakness of religion. And Christopher was able to explore those assets and weaknesses without judging, something I appreciated very much.
I also appreciated the fact he dealt with the changing issues of language. One of the major things you run into when studying religious texts is how language has shifted (or how words are translated).
It's nice to also see the Federation doing a "typical" (we don't have to resort to phasers) style story.