"Amazon's discounting policies" are the same as every other bookstore, they pay the publisher ~45% of the cover price for each book. Generally speaking, the publisher gets the same $$ whether you buy the book from Amazon or from Quirky-Bookstore-Full-of-Cats or from wherever.

If you buy directly from the publisher, then the publisher does get 100% of the price. And if they donate 50% of that to your local bookstore, they're still making more money than if you'd bought the book from that local bookstore. None of this has anything to do with Amazon.

I get that Amazon is bad for small independent bookstores (and for large chain bookstores too!), and I notice that the author just happens to own a small independent bookstore, so take his other complaints with a large grain of salt.