In my search for new books for possible review, I came across this great website. Small Press Distribution Books Online maintains an ongoing catalog of books (poetry, fiction, etc.) from “500+ Independent Presses!”
So if you can’t find that book from an “underrepresented literary community” that you’ve been dying to read, you should probably look here. It might not be at Amazon, and it definitely won’t be at your local Borders or Barnes & Noble.