Reddit reviews Palo Mayombe: The Garden of Blood and Bones

How deep do you want to go?

Look harder. It's out there, it's just not so easy to find as it doesn't sell well to a more general market. Amazon is a better bet than local spirit stores, which tend to be very 'white light'.
Slightly off-topic for r/wicca, but you might find this interesting if your curiosity runs that sort of way. A fascinating read.