So if I read a book for a day and stop at the 20% mark; then come back to it a month later and finish it, does the author then get 100%?

It seems likely to me that if user pays 10usd, Amazon will take it's cut like say 30 percent. Following 7usd will be divided amongst authors according to pages read. Each author will get 7 * pages read that month / total pages read that month.

For example if user reads one page of one book this month this author should get 7usd.

Medium works the same way except with reading time and maybe claps.

This at least is the most logical, fraudfree and fair way to do this.

Authors get paid monthly, approximately two months after the royalties are earned. So if you have a KU subscription and you read 20% of a KU book in January, the author will get paid for those pages in March, and then if you continue reading book and read the remaining 80% in February, the payment for the pages that you read in February will be included in their April statement.

It doesn't jive with Amazon's income from the book. I doubt that users pay for books on a percentage basis. So if someone buys a book, but doesn't read it, then Amazon gets the income, but isn't paying royalty on it.

That seems illegal.

Note: this thread is about Kindle Unlimited, which has a different monetization/payment model than regular Kindle ebooks. KU readers do not "buy" KU ebooks, any more than Netflix users "buy" the TV shows that they are streaming.

If someone pays $10/mo for access to a library of tens of thousands of books but doesn't actually read any of them, then Amazon gets income without having to pay royalties, in the same way that Netflix still gets your money if you subscribe but don't watch anything. This is true even if you decided to subscribe to KU/Netflix because "Oh, I should get around to reading Harry Potter/watching Stranger Things" and then don't get around to actually reading Harry Potter or watching Stranger Things. This is very much legal.

OK, that wasn't clear to me. So I guess it makes sense.

But does Netflix pay partial royalties on films, based on percentage viewed?

Unclear. We know how authors get paid for Kindle Unlimited because KDP is a self-publishing platform that anyone can use and Amazon has pages that explain everything when you go through the KDP signup process (plus reports from literally hundreds of authors who are enrolled in the program and post on forums/facebook groups about it). We have significantly less insight into the closed-door negotiations that happen between Netflix and Paramount Pictures to allow Indiana Jones movies to appear on Netflix; there are strategic reasons for both sides of the deal to want the details to be kept secret.