Enrolling in KDP Select enables authors and publishers to share in an annual fund, which at the current time is $11 million. If you choose this option, then your book is required to give the Kindle store exclusive rights for 90 days. Your percentage of the shared fund is based on how often your book is borrowed from the Kindle Owners’ Lending Library, which is exclusively available to Amazon Prime members who pay an annual fee for this benefit.
While your book is in this program, you cannot make it available for any other devices. Your Kindle version will be offered for the price you set in Amazon, but will be free to be borrowed for a 1-month period by Kindle Prime members. The benefit of this program is that if a prime member loves your book they will often go ahead and buy it later or recommend via word-of-mouth or leave a review. Currently, you also get 5 days’ worth of free advertising for every 90 days in the program. Once you join the program, the book will be exclusive to Kindle for 90 days. You can choose to have the 90 days automatically renew or not.