I just requested that Amazon pull all 23 of my books from the kdp select and Kindle Unlimited programs. I did this because I believed that Amazon greatly mislead us to get us to be part of the program. Their example when they rolled it out was that if you had a one hundred page book and one hundred people read it completely we would be paid 1000 dollars. That would be 10 cents per page. And while I did not think they would actually pay that I never assumed that what I considered a huge month, over 5200 pages would earn me less than a tank of gas on my Saturn Station Wagon. And that car has a small tank. In effect instead of a dime a page as they illustrated in their example they actually paid .005799 cents per page or for my 5200 pages read $30.15.
Now I realize at this point someone is going to jump in and tell me that they have made millions of dollars and all thanks to kdp select and Kindle Unlimited. And if that is true God bless you. That is what capitalism is all about. I may well be cutting off my nose to spite my face. After all $30.15 is better than nothing even if Amazon makes tens of millions of dollars while paying me a pittance.
The reason they changed they way we get paid, they said, is because people were writing shorter and shorter books and the customers were complaining. I believe they changed the way we are paid because they found out that they could make a bigger profit by cutting down on what they paid us independent authors.
You will have to decide if it is worth you time and effort of writing a good book and promoting it only to receive next to nothing while Amazon makes thousands of dollars off of your efforts.