Amazon will be making a big change that is now only a couple days away. Authors who have their e-books exclusive on Amazon by enrolling in KDP Select, making those books eligible to be borrowed through the Kindle Owners' Lending Library and Kindle Unlimited, will be paid per page instead of per book. This has caused a lot of controversy and consternation as writers try to figure out what they should do. Exacerbating the problem is the lack of hard details, such as exactly how pages will be calculated and how much is a likely per-page payment.
"Going wide" (making books available everywhere possible) instead of being exclusive to the Kindle platform has the obvious benefit of reaching readers who use other e-reading platforms. While the future of the NOOK platform has looked fairly shaky for awhile, there are many NOOK readers still in use, they're still being sold, and it's still a viable channel for now. Some authors have found Google Play Books to be a lucrative platform, and the Apple iBookstore is also a favored channel by many. Kobo is another e-reading platform that is apparently stronger outside the US. All other factors aside, the more platforms your book is available through, the more people you can reach.
Having books exclusive on Amazon also has benefits, because Amazon has long been a powerhouse for e-book sales and they are often where authors will have their best sales. Books that are only available (in e-book form) on the Kindle are given additional exposure by Amazon, so the sales potential of the Amazon powerhouse can directly benefit writers who get that extra exposure. On the other hand, if my own experiences (and experiences I've read about elsewhere) are any indication, the real value of that extra exposure—especially for writers who are not already making regular sales and are trying to build up to that point—has dropped drastically over the past few months. In the past, I was able to give away dozens or hundreds or even thousands of copies of books during a short free-download promotion, but lately I've been lucky to give away even one dozen.
There are many factors to consider, and a lot of uncertainty at this point. For a short while, Amazon will apparently allow people to pull their books out of KDP Select before the normal 90-day enrollment expiration, as a result of this change. That is what I'm leaning toward doing with the few books that I still have in KDP Select. You're welcome to share your plans in the comments.