Heyyyy I'm a committed Christian and a career publisher, I'm a mod at /r/publishing on reddit but besides that I'm not really a part of any other writing community, I just googled and found this place so just lurking around at the moment, looks pretty awesome here and I think I will be hanging around if you will have me. :)
I wanted to share this tool I made, as long as people search for books with keywords your keywords are going to be crazy important, and for me knowing how to properly find and utilize keywords was when my success kind of turned around back in the day as I learned the ropes of self-publishing. The discoverability of Christian novels seems worse than average, at least when I search for common search terms for Quaker books (I'm a Quaker) even some of the most respected and well known don't even show up unless I type in QUAKER and search through a dozen results, or an exact title. So I hope this helps, it takes advantage of the fact that Amazon provides SOME real search data from customers, in the form of the drop down suggestions. This is literally the only customer data they give us, and this tool utilizes that fact.
So you type in your keyword, and the tool will search around 50 combinations of the word to get all the relevant results, and display them for you. It only searches the kindle store, so all the results will only be searches made on Amazon by real customers in the kindle section. Repeated search terms are displayed in bold because they're more common. There's also a searchable category keyword section (the keywords you need to include to be listed in sub-categories) and a keyword organizer so you can separate into keyword strings that fill up all available space.
I hope this helps, all the best.