book: The Amazon Author Formula
Here's an amazing book to understand the back end of Amazon rankings.
If you've ever wanted to understand Amazon ranking, The Amazon Author Formula by Penny C. Sansevieri is a must-read. Available in KU.
Brick by brick, Sansevieri reveals how Amazon functions as a search engine, and how authors can use that knowledge to do what most authors don't do to get better visibility.
Using just the first part of the book, I researched new keywords/keyword phrases and new categories for my anthology of short stories. I haven't even gotten to the majority of the book yet!
ProTip: don't save your keywords on KDP if you plan on updating your categories and blurb, too—there's a 72 hour delay after you save, so just do it all at once.