It is quite possible to make the case that with KDP Select, Amazon has created a monopoly.  How so? Because their rules say that if you want your kindle edition to be a part of KDP Select, you cannot sell your book in any other electronic format or on any other website. If you already have the book listed with, say, Smashwords, you will have to remove it before you can join KDP Select. And that's not easy. Once other sites have copies of your book, they can simply refuse to comply and leave you hanging. Amazon asks for just a 90-day commitment, but their default renewal clause will renew you for another 90-day period without notification.  That just happened to me.  It is possible to opt out of the renewal, but only if you do so before your original period is up.  I missed mine by 1 day and am now committed for another 3 months. Can you withdraw your book from the program? Yes, you can do so at any time, but you cannot then sell it elsewhere until your current 90-day period is up.

Amazon now has a monopoly in another way as well.  It used to be that you could offer your book for free on another site and hope that Amazon would price-match the $0.00 price-tag, creating a free promotion on Amazon. Now, of course, if you try that, Amazon will come at you with an accusation that you have violated the terms of agreement you signed when you first  put a book on Amazon. Remember that little "I agree" box you checked without reading the small print? Yep, that one! You promised never to offer your book at a lower price than the one you set on Amazon. For any violation of Amazon's terms, you  and all your books can be banned for life.  Amazon has 32,000,000 books on their website.  They don't need you. But you definitely need them, since they control nearly three-quarters of all book sales. If you want to offer a free promotion of your book (and it's a really effective way to get more readers!), you can only do so as a member of KDP Select.

Are there any advantages for the author? Amazon promises that they will try harder to publicize your book if it's on KDP Select. One way they do so is to give you those 5 free promotion days any time you want them rather than just keeping your fingers crossed that Amazon will price-match a giveaway elsewhere. It's convenient -- and profitable -- to be able to choose your dates.

However, there are also great risks. When you give in to their restrictions, you cut out part of your reading audience.  I know I have readers who will only use Nook Books. Others don’t want a Kindle app on their iPads. They told me so emphatically when I announced that "Left by the Side of the Road" would only be available on KDP Select. Their reaction is important to me.  When I checked my sales figures for the past six months, I found that anywhere from 35% to 54% of all my sales came from Barnes and Noble. That may be a function of my particular genre, so don't take those figures as a general pronouncement. Still, I cannot afford to lose that large a segment of my readership.

Then there's the lending library. If you "belong," readers can borrow your book for as long as they want. And Amazon pays you a share of the enormous amount they set aside each month for that purpose ($700,000 in October.) However, the advantages of “borrowing” for free are pretty limited.  Prime customers only get one choice a month.  You want readers who read lots more books than that! In the interest of full disclosure, I have to admit that someone just borrowed my "Left by the Side of the Road", which sells for only $2.99.  I cannot for the life of me imagine why. If I could only get one book a month, I'd aim for something I really couldn't afford in any other way. My one transaction in the "Lending Library" does not contradict my general impression that I do not write the kind of books that do well as "borrows" rather than purchases.

The bottom line is that I suspect the sticks outweigh the carrots. I have three small volumes in KDP Select at the moment.  They are not big sellers and probably would not justify the cost and effort it would take to publish them over all channels, anyway. But my best-selling "Beyond All Price" and the award-winning "The Second Mouse Gets the Cheese" are both doing quite well on their own.  There are simply not enough advantages to KDP Select to convince me to limit them to a single sales channel.

And what will I do with my new book, "The Road to Frogmore" when it comes out at the end of the month?  I haven't yet made that decision.  I'm offering "Left by the Side of the Road" for free this Wednesday and Thursday in a heavily-promoted campaign.  The results may sway me one way or the other. I don know this, however. The only time I would offer a major book, such as this new novel, would be upon its first release, and I would do so only for that one 90-day period.  After that, free days lose their appeal and wide availability becomes more important.