Alex Newton runs K-Lytics, a data analysis service that looks at all things Amazon. He publishes monthly reports on different genres. The most recent one is on Science Fiction & Fantasy, 2020. These are paid reports because this data analysis is rather extensive and employs multiple people. Here’s what you’ll get in the report. I opened the SF one, but you get the same data for Fantasy as part of this one report.
One of the big takeaways from these reports is the sub-genre trend and why with minor tweaks, I put my hitman with a conscience thriller into vigilante justice sub-genre, in addition to the keyword analysis (I think this is better than what I’ve gotten from Publisher Rocket in regards to keywords).