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How Authors Get Paid in Kindle Unlimited
And is it worth it to include your book in KDP Select?
Amazon currently offers a service called Kindle Unlimited where, for a monthly fee (currently $9.99/month), readers can indefinitely borrow up to ten books so long as authors/publishers have chosen to include those books in Kindle Direct Publishing (KDP) Select.
From the author's standpoint, there are pros and cons to publishing your book in KDP Select. This article will explain what it is, how you get paid as an author, and whether or not it’s worth it to include your book.
How Do Authors Include a Book in the Program?
Authors publish their books to Amazon via Kindle Direct Publishing. After filling in the book information, you are given the opportunity to opt-in to KDP Select. This option appears on the final tab during this process, there is a box at the very top entitled, KDP Select Enrollment. When you click on the box, your book will be available for readers subscribed to Kindle Unlimited.

How Do Authors Get Paid?
On their website, Amazon does a decent job of explaining both the nuts and bolts of how money is delivered to you as well as how you get paid in KPD Select.
Essentially, a portion of the amount paid by KU subscribers is deposited into the “KDP Select Global Fund.” Each month, that fund is divided by the total number of “pages” read by every member of KU. The resulting number is the amount you get per page read of your e-books.
Total amount paid by KU subscribers/total number of pages read = Price per page.
About two weeks after the end of the month, Amazon sends out a notice via email informing you how much the total Select Global Fund was for that prior month, but not how many total pages were read.
You get paid toward the end of the subsequent month. So, for instance, if you earned $5,000 in January, you’d see that money hit your bank account somewhere toward the end of March.